Air fuel ratio readings on boost and rollers from SC?
#62
Originally Posted by Neilo
and are they still cased in UK heads?
and is the box still UK 5 speed? or a 6 speed conversion?
and is the box still UK 5 speed? or a 6 speed conversion?
#65
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Joined: Jul 2003
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From: Behind the wheel of a Time Attack R33 GTR
no im running 355lbft on a newage UK box (2003, whereas this car is a bugeye AFAIK) but i have also used mine with a 75 shot of nitrous on top which would have made the torque jump up to around 460+lbft on the drag strip.
It has also been used on the track since then.....they arent as fragile as people make out. They get destroyed by people that drive badly IMO.
New turbo on the way to raise the power level to 400-420lbft, we will see how it copes then, but again, i still think its down to the driver as to how long the box will last.
Dont get me wrong, its not indestructible and i may have got lucky, but i dont think they are as weak as people make out.
It has also been used on the track since then.....they arent as fragile as people make out. They get destroyed by people that drive badly IMO.
New turbo on the way to raise the power level to 400-420lbft, we will see how it copes then, but again, i still think its down to the driver as to how long the box will last.
Dont get me wrong, its not indestructible and i may have got lucky, but i dont think they are as weak as people make out.
Last edited by Neilo; 19 July 2006 at 03:27 PM.
#66
Cams are piper 285 profile on new age wrx heads, reworked and lips removed for 2.5L bores etc.
RE Pat, I did expect lumpy running but not for it to cut out (three times already in about 150 miles) and run almost constant engine misfires! Will resolve this when I can and report back.
RE Pat, I did expect lumpy running but not for it to cut out (three times already in about 150 miles) and run almost constant engine misfires! Will resolve this when I can and report back.
#69
Was offered this profile at excellent price so jumped for it! Knew there would be some draw backs but also knew she'd go like stink from about 2500 and produce lots of power .
Still cant understand why my map is so different to gaf's on fuel and boost .
Still cant understand why my map is so different to gaf's on fuel and boost .
#71
Originally Posted by swisstonihasher
Was offered this profile at excellent price so jumped for it! Knew there would be some draw backs but also knew she'd go like stink from about 2500 and produce lots of power .
Still cant understand why my map is so different to gaf's on fuel and boost .
Still cant understand why my map is so different to gaf's on fuel and boost .
You may have heard of blue print engines, this is when the tolerances are matched t make sure the engine is well balanced etc
age, ondition, even slight density changes in materials can make slight changes.
#73
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Joined: Jul 2003
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From: Behind the wheel of a Time Attack R33 GTR
i guess though if it was offered as a 450/450 package then the end result should be 450/450, not 440/420, the only variable to this for me is those cams....if they are a bugger to map...then perhaps they are best removed..
(i realise that only the turbo was used from SC's 450 package mind you)
(i realise that only the turbo was used from SC's 450 package mind you)
#74
if there race cams then car will run like a bag o **** on idle, guy across the roads races ferraris and he's got a full race spec 360, sounds like its gonna spit pistons out till he revs it, then o boy, car **** alert lol.
#75
When I looked at the turbo setup to go on my car, it was quoted at 450/480 but my oe ecu and no boost controller would limit things. The 450/480 setup is quoted without water injector or wild cams.
Things are going to happen soon anyway, so will report results.
Re the cams..they're 285's so not full on race but does make car shift like h8ll .
I'm going to have the EGT's lowered for sure and more boost , I hope, I'm not happy running engines at 915-918 deg constantly when going for it and the odd 935 when in top gear.
Things are going to happen soon anyway, so will report results.
Re the cams..they're 285's so not full on race but does make car shift like h8ll .
I'm going to have the EGT's lowered for sure and more boost , I hope, I'm not happy running engines at 915-918 deg constantly when going for it and the odd 935 when in top gear.
#76
Hi,
My cams are standard V4 sti, no water injection, allthough its actually fitted just never had time to plumb it in, the pistons are wiseco with our own crown design, custom crower rods, managment is autronics, no air flow meter to worry about.
As for tickover its not been a problem until this hot weather where I have had more stalling issues on my way home than swisstonihasher has had since he got his car back.
Daft cams or aftermarket ecus there allways seems to be a downside like high tickover, lumpy tickover somtimes no tickover at all, the quest for big power goes on.
Cheers
Kev.
My cams are standard V4 sti, no water injection, allthough its actually fitted just never had time to plumb it in, the pistons are wiseco with our own crown design, custom crower rods, managment is autronics, no air flow meter to worry about.
As for tickover its not been a problem until this hot weather where I have had more stalling issues on my way home than swisstonihasher has had since he got his car back.
Daft cams or aftermarket ecus there allways seems to be a downside like high tickover, lumpy tickover somtimes no tickover at all, the quest for big power goes on.
Cheers
Kev.
#77
Originally Posted by swisstonihasher
I'm going to have the EGT's lowered for sure and more boost , I hope, I'm not happy running engines at 915-918 deg constantly when going for it and the odd 935 when in top gear.
You are running approx 1.5 bar the ecutech set up cant see above 1.55 bar it will try to control it but only with approximation this is why I recomended a boost controler and to compliment it a decent ecu.
Have you not digested the post from Pat ??????
Cheers
Kev.
#78
Yes Kev, Pat's comments on EGT's still doesn't make me happy with my setup (it seems to be his word against many on 900+ temps). The pure fact is that people like Harv etc have had engines pop at those temps . Project on hold now till I'm ready to resolve everything .
#79
Originally Posted by swisstonihasher
Yes Kev, Pat's comments on EGT's still doesn't make me happy with my setup (it seems to be his word against many on 900+ temps). The pure fact is that people like Harv etc have had engines pop at those temps . Project on hold now till I'm ready to resolve everything .
#80
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Joined: Jul 2003
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From: Behind the wheel of a Time Attack R33 GTR
Originally Posted by Tidgy
sounds like first port of call is to sort out decent ecu and boost controler.
Was interested to read the supposed 1.55 bar limit on ecutek....(of an accurate nature)
#81
not the first time i've heard it by any stretch of the imagination, well bit about norm ecu not being able to cope with increase in capacity of 25% and then other bits as well, tis all a bit over my head once it gets to that stage tbh.
#82
I cannot help but chuckle at the lack of knowledge displayed here. For someone to say "930 degrees EGTis likely to break the engine" is a bit like saying "driving it in the UK is likely to break the engine". It's a completely unqualified statement and very deceptive.
Just where is this magical 930 supposed to be measured ??? At the exhaust port ? At the collector ? At the turbo entry ? In the downpipe ? The fact of the matter is that EGT is a function of where it's measured. You may lose 150 degrees in the turbo, so 800 in the downpipe may well be 950 at the turbo entry, which may be 1050 at the exhaust port. A little knowledge is a dangerous thing! Some people might say that running 13.3:1 AFR on full chat is too lean. Funny, then, that the winner of this year's LMP2 catergory at Le Mans was running that, for about 24 hours, but still managed to win According to the "experts" on here that should have melted! A little knowledge is a dangerous thing.
Just for clarification, the ECUTEK system can see boost pressures up to 1.72 bar, but it is unwise to set a boost target close to this when the ECU is controlling the boost itself because it cannot see overboost conditions. Say we set a 1.65 bar boost target and we get 1.85 bar, we'de actually only see 0.07 bar of overboost rather than 0.20 because anything over 1.72 just reads 1.72... on the other hand, if we set a target of 1.50 bar and we get 1.70 bar, we can actually see 0.20 bar of overboost. If we can see an undesirable condition we can do something about it; if we can't see it we can't do something about it. This is why we tend to keep boost pressures down when running ECUTEK without additional boost controlllers.
On Kev's car we have an Autronic ECU that can see 2.4 bar of boost and it's running an APEXi AVC-R boost controller. We can run 1.7 bar because both the ECU and the boost controller can see the boost. If we suddenly get 1.9 bar and the controller cannot bring it back down, the ECU sees it and will fuel cut to protect the engine. We can't do this on ECUTEK because we can't see 1.9 bar, only 1.72, so the highest fuel cut we can set is 1.72 bar, and if we set the boost target at 1.65 and got an occasional slight overshoot then we'de get irritating cuts. It is possible, however, to replace the stock boost pressure sensor with ECUTEK and thus it is technically feasible to go beyond 1.72 bar, but it's an additional cost option.
For additional clarification, the "450/450 package" is for engines that we build to our specifications, the turbo suplied will produce approximately those figures with our choice of components, but as a turbo on its own, "your mileage may vary".
Regarding stalling, that's another foible of MAF based systems and is related to reading airflow that does not exist as the engine returns to idle. Vent to atmosphere dump valves and FMICs are the biggest culprits, adjusting the dump valve so that it requires a reasonable manifold vacuum AND a bit of boost in the FMIC pipework can reduce the issue, as can returning the engine to idle more gently. Big ball bearing turbos have big shaft inertia and create all sorts of erroneous MAF readings, that's part of the reason for MAFSIM and the reason that none of the big power PowerFC cars run MAFs....
Cheers,
Pat.
Just where is this magical 930 supposed to be measured ??? At the exhaust port ? At the collector ? At the turbo entry ? In the downpipe ? The fact of the matter is that EGT is a function of where it's measured. You may lose 150 degrees in the turbo, so 800 in the downpipe may well be 950 at the turbo entry, which may be 1050 at the exhaust port. A little knowledge is a dangerous thing! Some people might say that running 13.3:1 AFR on full chat is too lean. Funny, then, that the winner of this year's LMP2 catergory at Le Mans was running that, for about 24 hours, but still managed to win According to the "experts" on here that should have melted! A little knowledge is a dangerous thing.
Just for clarification, the ECUTEK system can see boost pressures up to 1.72 bar, but it is unwise to set a boost target close to this when the ECU is controlling the boost itself because it cannot see overboost conditions. Say we set a 1.65 bar boost target and we get 1.85 bar, we'de actually only see 0.07 bar of overboost rather than 0.20 because anything over 1.72 just reads 1.72... on the other hand, if we set a target of 1.50 bar and we get 1.70 bar, we can actually see 0.20 bar of overboost. If we can see an undesirable condition we can do something about it; if we can't see it we can't do something about it. This is why we tend to keep boost pressures down when running ECUTEK without additional boost controlllers.
On Kev's car we have an Autronic ECU that can see 2.4 bar of boost and it's running an APEXi AVC-R boost controller. We can run 1.7 bar because both the ECU and the boost controller can see the boost. If we suddenly get 1.9 bar and the controller cannot bring it back down, the ECU sees it and will fuel cut to protect the engine. We can't do this on ECUTEK because we can't see 1.9 bar, only 1.72, so the highest fuel cut we can set is 1.72 bar, and if we set the boost target at 1.65 and got an occasional slight overshoot then we'de get irritating cuts. It is possible, however, to replace the stock boost pressure sensor with ECUTEK and thus it is technically feasible to go beyond 1.72 bar, but it's an additional cost option.
For additional clarification, the "450/450 package" is for engines that we build to our specifications, the turbo suplied will produce approximately those figures with our choice of components, but as a turbo on its own, "your mileage may vary".
Regarding stalling, that's another foible of MAF based systems and is related to reading airflow that does not exist as the engine returns to idle. Vent to atmosphere dump valves and FMICs are the biggest culprits, adjusting the dump valve so that it requires a reasonable manifold vacuum AND a bit of boost in the FMIC pipework can reduce the issue, as can returning the engine to idle more gently. Big ball bearing turbos have big shaft inertia and create all sorts of erroneous MAF readings, that's part of the reason for MAFSIM and the reason that none of the big power PowerFC cars run MAFs....
Cheers,
Pat.
#84
I have been told that under grief the egt went up to 900 and under serious grief it once hit 915 degrees, I agree its not long before valves will melt at 935 if you keep your toe in, but thats why we have gauges they tell us when to back off, if we care to take notice.
My mapper is quite happy with 900 degrees and says that for very very short spells 950 degrees.
I have asked the owner to take a steady drive down and we can re-run it on the dyno overlaying the graphs to see if it has actually leaned off, we await his response.
Cheers
Kev.
My mapper is quite happy with 900 degrees and says that for very very short spells 950 degrees.
I have asked the owner to take a steady drive down and we can re-run it on the dyno overlaying the graphs to see if it has actually leaned off, we await his response.
Cheers
Kev.
What I know is that AFRs of 12:1 is very weak and with rising EGTs above 915 C VERY worrying on a Classic road Subaru.
If after mapping you have to rely on guages to tell you when to back off, there is something far wrong.
For a start, how many people run EGT guages?
Are your average customers told when to back off?
What if they miss the back off point, assuming they have the right guages, know the back off point and can actually drive at full boost, head in the cabin.
Surely the car should be mapped safely for the running it is likely to do and as far as I am concerned that excludes EGTs of 950C.
Daft cams
Pat made reference to my experience where I concluded that 930 c EGT was courting trouble. That is my carefully assessed observation. He also made reference to actual and perceived AFRs.
Rather than allude to two different AFRs share your knowledge and enlighten us.
Chuckle as much as you want but if you think that mapping customer cars like this ;
My mapper is quite happy with 900 degrees and says that for very very short spells 950 degrees
Then I guess you will have had more than your fair share of map related engine failures.
FYI my EGTs are measured at the collector, the earliest opportunity to measure all combined gas temps. (Ialso have a 4 branch exhaust manifold to measure individual cylinder exhaust temps.) I can also tell you that at 930C there is the risk of loosing the EGT probe tip which will then exit via the turbo exhaust with probable expensive damage.
Reference is made to Le Mans. Let's just stick to average road going Scoobies, unless otherwise specified, which is what this bbs is about.
the winner of this year's LMP2 catergory at Le Mans was running that, for about 24 hours, but still managed to win According to the "experts" on here that should have melted! A little knowledge is a dangerous thing.
Quite simply, AFRs on a road going Subaru of 12:1 are very worrying as are rising EGTs as described above.
Last edited by harvey; 21 July 2006 at 11:14 PM. Reason: AFRs not EGTs
#85
Harvey you have taken Kev out of context here he meant we did not map the car with the power graph that was posted by wrx rich.
asking a customer to come back to check things this is simple Garage etiquette if they have any queries.
cheers
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asking a customer to come back to check things this is simple Garage etiquette if they have any queries.
cheers
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#86
Can i ask what fuel pump is used?
From what i read, briefly and not all of it tbh, the problem sounds similar to one encountered on Alan Bell's car, where the fuel pump just couldnt supply the fuel required at that boost level!
Is this the car that was at the clinic a few weeks back, roughly the 22nd June, which had major problems with injectors and fueling???
Newage car with a 2 tone blue paint, and all sorts of gubbins attached to it?
From what i read, briefly and not all of it tbh, the problem sounds similar to one encountered on Alan Bell's car, where the fuel pump just couldnt supply the fuel required at that boost level!
Is this the car that was at the clinic a few weeks back, roughly the 22nd June, which had major problems with injectors and fueling???
Newage car with a 2 tone blue paint, and all sorts of gubbins attached to it?
#87
Originally Posted by P20SPD
Can i ask what fuel pump is used?
From what i read, briefly and not all of it tbh, the problem sounds similar to one encountered on Alan Bell's car, where the fuel pump just couldnt supply the fuel required at that boost level!
Is this the car that was at the clinic a few weeks back, roughly the 22nd June, which had major problems with injectors and fueling???
Newage car with a 2 tone blue paint, and all sorts of gubbins attached to it?
From what i read, briefly and not all of it tbh, the problem sounds similar to one encountered on Alan Bell's car, where the fuel pump just couldnt supply the fuel required at that boost level!
Is this the car that was at the clinic a few weeks back, roughly the 22nd June, which had major problems with injectors and fueling???
Newage car with a 2 tone blue paint, and all sorts of gubbins attached to it?
as for fuel pump its somthing he had fitted else where, although it seemed to supply enough fuel, if its leaned off since we mapped it then maybe it will need the Alan bell mod using a bosch pump and a contoller designed in house to handle the current demand, which is why I have invited the owner to pop back and we will run the car again, overlaying graphs to check if it has acctually leaned off .
Cheers
Kev.
Last edited by The Gaffer; 19 July 2006 at 11:34 PM.
#88
The confusion about who has mapped it etc is because people aren't in posession of the full facts. Tony was an indirect customer of mine from way back when, and I had mapped the car previously as a 2 litre. When he fitted the 2.5 litre and needed it mapping he contacted me to see if I could help. He also had some other things that needed doing to the car so I suggested the simplest solution was to bring the car to Scoobyclinic and for them to carry out the mechanical work, then for the car to go onto the dyno for mapping. In this sense, it's not a Scoobyclinic map, although it was mapped at Scoobyclinic.... they provided the dyno facility but not the mapping service per se.
With regard to Kev suggesting Tony brings the car back for us to have a look at it, that's just good customer service. It might not be his "problem" or responsibility but he cares enough to make it his "problem" because Tony is also a Scoobyclinic customer, even if the specific service Tony perceives he has a problem with was not provided by Scoobyclinic per se.
Harvey's statement that 12:1 is too weak may indeed be true, if this were a standard engine, but this is far from standard, and therefore you cannot apply the same "rules" to this engine you might to another, standard engine. Had it been a standard engine then it would not have been let out the door running this appearance AFR. Because it is not a standard engine, its appearance AFR will have a different correllation to actual AFR, its EGT characteristics will not be the same as a stadard engine under the same conditions. What may be correct for one configuration may be way off the mark for another. In any event, EGTs up to 950 are not an issue.
Gauges are wonderful double edged swords..... Having a gauge to tell you when to back off is not necessarily symptomatic of an issue with the mapping, it could just be an aknowledgement of an inadequacy in the car. For example, any Subaru 2.5 litre turbo motor that does not have an additional oil cooler will suffer high oil temperatures when under load. This is true even of standard cars as they come out of the factory. But most people are blissfully unaware of the fact their oil is very hot until they fit a gauge. They drive around without a care in the world for the oil temperature because they don't know it is getting hot. But, strangely, Subaru don't seem too concerned about it. After all if it was a problem, then surely they'de get a lot of warranty claims, and that would put a serious dent in the bottom line. But still they choose not to fit them. So who is actually "right" ? The owner who has a gauge, and exercises mechanical sympathy by backing off when they see the oil temps get rather too tepid, or the owner who doesn't have a gauge and just drives the car. It doesn't take a genious to figure out which one is having more fun. However, the "experts" (and ironically I would concur) would have you believe that the oil is too hot... perhaps they should try telling that to Fuji Heavy Industries ? Sometimes accepted wisdom is no substitute for experience, and you could infer that because FHI have chosen not to address this perceived "problem", it isn't actually a problem at all, it's just that accepted wisdom isn't always right.... or maybe the world really is flat after all ?
Having gauges allows you to decide whether or not you're happy with the prevailing engine conditions. You are free to act on them any which way you want. Just because you decide that the reading you're seeing is too high does not mean that the engine shares your view on the situation. It might have gotten upset some time prior to you restraining yourself, or it might be quite happy to keep going where you are not.
When mapping, the basic premise is always to make the car safe under any conditions that it is realistically likely to encounter within the constraints of the hardware present. If, for example, the customer has chosen not to fit an oil cooler, then it is their responsibility to ensure they don't kill the thing by driving it too hard, because the only way to ensure that they cannot inadvertently kill it by a lapse of concentration is fundamentally at odds with the purpose of getting the engine mapped; it would be necessary to de-tune the engine below the level it leaves the factory to ensure that it cannot possibly get the oil to a temperature that would be deemed as unsafe. In this instance we are talking about EGTs, and as already stated, it is not necessary to lift off at 913 degrees, it's just that some people seem to think it is.
With regards to cams, I'de call 285 degrees duration on a turbo cam fairly "hot". Considering Harvey achieved his claimed 585 BHP with mere 242 duration cams, and Prodrive won the WRC with a mere 280 duration cam profile, I think it would be fair to call a 285 duration cam moderately wild. That's not to say you cannot achieve an acceptable idle on such a cam. I remember using some WRC cams and getting a beautiful idle at 900RPM. And I also recall using the same profile in an engine that has generated the highest torque figure ever recorded for a Subaru engine in the UK, but that wouldn't idle at anything below 1200RPM. The great thing about the Subaru engine is that it's a quad cam motor, which means that you can vary the LSA. You can set them up so that the engine is incapable of idling below 1500 RPM, or you can set them so that it is as smooth as silk at 800RPM. But one thing that you will learn, is that in order to exploit the cam, to get your money's worth out of it, you won't have much of an idle left low down. And of course cam timing has a knock on effect on appearance AFR. And it has a knock on effect on EGT. Run a lot of overlap and you'll get a lot of fresh air taking the express route from the inlet straight out the exhaust, distorting the AFR readings. Run a fair amount of advance on the exhaust cam and say hello to wild EGTs.... if you open up the exhaust valve early then you'll get more of the still-burning-and-fscking-hot combustion gasses making a speedy exit into the headers during the blowdown event and you see the EGT gauge go up accordingly. On the flipside, you get less heat flux into the valve at the end of the exhaust stroke and with a lot of overlap the exhaust valves get a good hit of fresh air to cool them down even before they get back to the seat to cool down. So it's entirely possible to have an increase in net EGT without having an increase in net exhaust valve temperature. Which brings us back to the point about accepted wisdom. Just because people believe that the a standard engine might experience issues running aroung 950 degrees EGTs doesn't mean that this engine is in any way constrained by the same accepted wisdom that is applicable to a conventional engine. Just to put the cat among the pigeons, I've seen cruise EGTs over 1100 degrees C, but for some bizarre reason the exhaust valves didn't melt. Could it be voodoo magic ? No, it's just plain old physics.
I find it quite interesting that people who have not either a) taken the time to actually try playing around with different cam profiles and timings themselves or at least b) read and learnt about the way that such variables might affect the operation of an engine and how it might alter the appearance values you might expect to observe should presume to take it upon themselves to preach about what is right and what is not, when their own inexperience precludes them from making any such assertions from any viable point of authority. I don't pretend to know everything about engines, and I am always happy to learn from those whose experience exceeds my own and who are generous to share their acquired wisdoms with me. I cannot offer a concrete guarantee that something won't go wrong, no more so than Subaru can offer a concrete guarantee that nothing will ever go wrong with a standard car (there would be no need for Subaru Assist if that were the case, but its very existence is a testament to the fact that things can and do go wrong), but if I was at all concerned about the AFR or EGT then it wouldn't have left with those readings.
Cheers,
Pat.
With regard to Kev suggesting Tony brings the car back for us to have a look at it, that's just good customer service. It might not be his "problem" or responsibility but he cares enough to make it his "problem" because Tony is also a Scoobyclinic customer, even if the specific service Tony perceives he has a problem with was not provided by Scoobyclinic per se.
Harvey's statement that 12:1 is too weak may indeed be true, if this were a standard engine, but this is far from standard, and therefore you cannot apply the same "rules" to this engine you might to another, standard engine. Had it been a standard engine then it would not have been let out the door running this appearance AFR. Because it is not a standard engine, its appearance AFR will have a different correllation to actual AFR, its EGT characteristics will not be the same as a stadard engine under the same conditions. What may be correct for one configuration may be way off the mark for another. In any event, EGTs up to 950 are not an issue.
Gauges are wonderful double edged swords..... Having a gauge to tell you when to back off is not necessarily symptomatic of an issue with the mapping, it could just be an aknowledgement of an inadequacy in the car. For example, any Subaru 2.5 litre turbo motor that does not have an additional oil cooler will suffer high oil temperatures when under load. This is true even of standard cars as they come out of the factory. But most people are blissfully unaware of the fact their oil is very hot until they fit a gauge. They drive around without a care in the world for the oil temperature because they don't know it is getting hot. But, strangely, Subaru don't seem too concerned about it. After all if it was a problem, then surely they'de get a lot of warranty claims, and that would put a serious dent in the bottom line. But still they choose not to fit them. So who is actually "right" ? The owner who has a gauge, and exercises mechanical sympathy by backing off when they see the oil temps get rather too tepid, or the owner who doesn't have a gauge and just drives the car. It doesn't take a genious to figure out which one is having more fun. However, the "experts" (and ironically I would concur) would have you believe that the oil is too hot... perhaps they should try telling that to Fuji Heavy Industries ? Sometimes accepted wisdom is no substitute for experience, and you could infer that because FHI have chosen not to address this perceived "problem", it isn't actually a problem at all, it's just that accepted wisdom isn't always right.... or maybe the world really is flat after all ?
Having gauges allows you to decide whether or not you're happy with the prevailing engine conditions. You are free to act on them any which way you want. Just because you decide that the reading you're seeing is too high does not mean that the engine shares your view on the situation. It might have gotten upset some time prior to you restraining yourself, or it might be quite happy to keep going where you are not.
When mapping, the basic premise is always to make the car safe under any conditions that it is realistically likely to encounter within the constraints of the hardware present. If, for example, the customer has chosen not to fit an oil cooler, then it is their responsibility to ensure they don't kill the thing by driving it too hard, because the only way to ensure that they cannot inadvertently kill it by a lapse of concentration is fundamentally at odds with the purpose of getting the engine mapped; it would be necessary to de-tune the engine below the level it leaves the factory to ensure that it cannot possibly get the oil to a temperature that would be deemed as unsafe. In this instance we are talking about EGTs, and as already stated, it is not necessary to lift off at 913 degrees, it's just that some people seem to think it is.
With regards to cams, I'de call 285 degrees duration on a turbo cam fairly "hot". Considering Harvey achieved his claimed 585 BHP with mere 242 duration cams, and Prodrive won the WRC with a mere 280 duration cam profile, I think it would be fair to call a 285 duration cam moderately wild. That's not to say you cannot achieve an acceptable idle on such a cam. I remember using some WRC cams and getting a beautiful idle at 900RPM. And I also recall using the same profile in an engine that has generated the highest torque figure ever recorded for a Subaru engine in the UK, but that wouldn't idle at anything below 1200RPM. The great thing about the Subaru engine is that it's a quad cam motor, which means that you can vary the LSA. You can set them up so that the engine is incapable of idling below 1500 RPM, or you can set them so that it is as smooth as silk at 800RPM. But one thing that you will learn, is that in order to exploit the cam, to get your money's worth out of it, you won't have much of an idle left low down. And of course cam timing has a knock on effect on appearance AFR. And it has a knock on effect on EGT. Run a lot of overlap and you'll get a lot of fresh air taking the express route from the inlet straight out the exhaust, distorting the AFR readings. Run a fair amount of advance on the exhaust cam and say hello to wild EGTs.... if you open up the exhaust valve early then you'll get more of the still-burning-and-fscking-hot combustion gasses making a speedy exit into the headers during the blowdown event and you see the EGT gauge go up accordingly. On the flipside, you get less heat flux into the valve at the end of the exhaust stroke and with a lot of overlap the exhaust valves get a good hit of fresh air to cool them down even before they get back to the seat to cool down. So it's entirely possible to have an increase in net EGT without having an increase in net exhaust valve temperature. Which brings us back to the point about accepted wisdom. Just because people believe that the a standard engine might experience issues running aroung 950 degrees EGTs doesn't mean that this engine is in any way constrained by the same accepted wisdom that is applicable to a conventional engine. Just to put the cat among the pigeons, I've seen cruise EGTs over 1100 degrees C, but for some bizarre reason the exhaust valves didn't melt. Could it be voodoo magic ? No, it's just plain old physics.
I find it quite interesting that people who have not either a) taken the time to actually try playing around with different cam profiles and timings themselves or at least b) read and learnt about the way that such variables might affect the operation of an engine and how it might alter the appearance values you might expect to observe should presume to take it upon themselves to preach about what is right and what is not, when their own inexperience precludes them from making any such assertions from any viable point of authority. I don't pretend to know everything about engines, and I am always happy to learn from those whose experience exceeds my own and who are generous to share their acquired wisdoms with me. I cannot offer a concrete guarantee that something won't go wrong, no more so than Subaru can offer a concrete guarantee that nothing will ever go wrong with a standard car (there would be no need for Subaru Assist if that were the case, but its very existence is a testament to the fact that things can and do go wrong), but if I was at all concerned about the AFR or EGT then it wouldn't have left with those readings.
Cheers,
Pat.
Last edited by pat; 20 July 2006 at 03:31 AM.
#90
Then I guess you will have had more than your fair share of map related engine failures.
Cheers,
Pat.