switched on dyno dynamics between 3rd and 4th many times to check and it makes little or no difference.

the reason for 3rd on your car Tim is that it was being mapped on the rollers not just a power run and the extra heat of repeated runs is reduced using 3rd as the run through the gear is shorter.

Yes in 4th is may have spooled slightly earlier

Simon

 

Excuse my ignorance but what exactly does this mean? Do you mean boost level varies between 0.4 and 1.0 at full throttle or something else?

 

OK - thanks Simon, was getting worried for a moment The spool is better on the road than on the graphs, but still not what it should be IMHO as per earlier posts - not down to the mapping I hasten to add!

 

it will always be earlier on the road..

the boost / fuelling / spool point when the car was on the rollers this time was identical to how I left it.. first run we had boost and AFR on the monitor and the previous graph and they matched exactly.. Len and I thought oh dear no change..
then checked the torque and it had jumped 90lb..

Simon

 

Do you think the on-the-road spool I've reported is to be expected for this sort of set up? Am I living in cloud cuckoo land thinking it should be 300-400rpm lower?

 

tbh I would have hoped for slightly earlier.

Simon

 

OK - thanks Simon I'll talk to Iain on Monday and see what he thinks.

 

Completely agree Paul, something I too have noted in the past with mid sized hybrids.

 

Jesus.... I wish my car would gain 90lb without doing anything.

Any ideas how you think that could of happened?

 

no idea.. the car had the turbo checked and Iain found the cracks in the downpipe and that was repaired etc inbetween

Simon

 

Probably sucking eggs etc. But you are sure you arnt moving the car post an ECU Reset until the fuel pump speed has dropped? If you don't wait that initial period the AVCS switches off.

My MY05 JDM STi was the first to have the MegaROM coding, prior to that it had only been loaded on the Spec C, at the time EcuTek weren't sure it would work. It did of course and is well worth using, but there isnt a lot of history of using this coding on the none spec C version of MY05.

 

I also agree with Paul and Martyn Turbos on the whole are consistant in what they can ultimately flow. Engines specs aren't.

Most of the JDM cars we have though the door have the MegaRom installed prior to resell including MY05 & MY06 STI's and Spec C. If you can get it to work its definately worth it.

Shaun the only thing we did was repair the downpipe are replace the gaskets.

 

I know two local (non Spec C) '05 JDM STi's that use megarom successfully, so I agree it is something odd with mine, but I'm sure we'll sort it.

We now know that the rollers used for my runs was not setup right - the operator has only recently acquired the dyno so is still learning how to use it.

The power figure is correct but the rpm scale and torque figure is wrong so can't be relied on. I suspect the torque is about 30ftlb's lower - so we're looking at a 460/450 result perhaps.

The on-the-road spool is also - to me - a symptom of something not being right.

I've had a very useful and supportive email from Iain (thanks Iain ) and I will now a) drive it for a while to see what it's like after a few days and b) get it dyno'd elsewhere so we have a good datum point.

I will then talk to the engine builder about possible causes, but the #1 candidate in my mind is the Tomei headers. We all know the OEM ones are excellent and I only changed mine so I could sell the Vf37, headers and up-pipe as an upgrade package. Which I've now done.

So, if anyone has a set of OEM twinscroll headers going cheap, or that I could borrow, I will try and arrange a swap so I can check the effect on spool.

I know we'll get there - but to re-iterate; the car is very enjoyable to drive and obviously no comparison to a year ago so my continued thanks to Len, Simon and Iain

 

Tim,
Try giving API a call for a set off oe twinscroll headers. They did have some sets, but was some time ago I admit.

 

Thanks Shaun...why wait until tomorrow to phone; email is already sent

 

Usual routine enables cams on original rom, but megarom wont.
Used megarom on a number of cars without this issue

 

Fpan u have pm.

 

Sounds like classic (although quite extensive in this case by up to .6bar) surge from the OE twinscroll, when bashing an induction kit on. If you have a boost gauge, you can see it rapidly wavering around like it is having a fit.

 

A brief update after a lunchtime drive with a work colleague.

Spool to full boost's about 200rpm lower than I reported - much easier having someone else looking at the gauge. So 1.7bar is at about 3400rpm not 3600 as I previously reported.

Various dialogues with Iain Litchfield and Simon have ruled out the cat as a reason for late spooling, although it probably accounts for 460bhp rather than the 480 the turbo's rated for, but the headers may indeed be accounting for the spool issue.

I will also get another dyno plot done, since my results are misleading due to (fully understandable) human error when the run was made. C'est la vie

I have located a second hand set of OEM headers and up-pipe, waiting on price confirmation, but I also have a tentative offer of a loan of a set I will probably bite on the bullet and have them swapped over to see what difference they make.

Simon is also still keen to look at the megarom issue as that should improve the overall package as has been pointed out.

So, I'm feeling a bit more optimistic than I was over the weekend, as I now have a plan coming together to investigate the issues scientifically

And the comment from my passenger - who has modified his series 3 XJ12 jag by adding a supercharger, amongst other things, giving 520whp, and also has a 500bhp+ drag bike that he races - was that it "certainly goes doesn't it" He then said it needed another 100bhp and asked when I was planning to get it

 

Been doing some research....I'm like a dog with a bone on this

Stock OEM headers: main header pipes diameter 42.7mm; up-pipe 42.7mm
Tomei 2.0l headers: main header pipes diameter 38mm; up-pipe 42.7mm.
Tomei 2.5l headers: same as OEM headers

Since I have the 2.0l Tomei headers, there is an obvious difference here due to the smaller pipe diameter .

Something that definitely needs to be explored and eliminated - and, hopefully, I can get away without having to replace the up-pipe for this experiment as it's the same diameter...whether it's the same fitting remains to be seen.

 

best to have a plan

That's after the next "tweak" LOL

Could be 30-50bhp more, so nearly the 100bhp

Tim Good luck hell this "modding" is easy ain,t it

 

Tim,
I suspect the smaller diameter header for the 2ltr is to increase gas speed, whereas with the 2.5 you would benefit from the OEM diameter, as you will potentially be requiring to flow more air.

I told you there was nothing wrong with the OEM tubular headers.

 

Never questioned it...only swapped out because the Tomei ones had good rep, and it allowed me to sell on the VF37/headers/up-pipe as an upgrade package. With hindsight, probably a wrong move, but hey ho

 

As Shaun says the O/E twin scroll is very good and needs very little fettling to perfect.

A word on benchmarking turbos. It is best to stick to the same rolling road and always stick to the same gear. Different rolling roads will give differing results when run in different gears, particularly for torque which is what the rolling road is measuring in the first place. Many rolling roads are accurate enough to pick up on changes in tyre pressure alone.
Running on DynoDynamics R.R. you will get a slightly higher power figure running 3rd than 4th but slower spool obviously in 3rd or less power in 4th but quicker turbo spool.
I think it is best to run in the gear that is most direct, closest to 1:1, usually 4th on a five speed and 5th on a six speed.
Trying to compare results between two different types of RR is a waste of time eg Dastek and DynoDynamics. However I have found that results from DynoDynamics rolling roads at different locations are fairly consistent providing the same gear is used.

 

Having mine re-run on a DynoDynamics RR on Thursday so I can get a correct datum point to compare against as I make changes in the coming weeks.

Harvey - don't suppose you've got a set of OEM twin scroll headers and up-pipe for sale, have you?

 

Think i've got some twinscroll headers and an up pipe somewhere. Will check for you and get back to ya.

 

 

Sorry, nothing twin scroll. These need very little done to them so it is straight off the car, brief tidy up and straight back on.

 

Harvey...when you say
I'm not 100% sure what you mean?

 

I think Harvey, means that he's not got any hanging about due to them not requiring much work when they're off compared to non twin scroll headers.