Guys - It hads to be said that David only managed 360bhp out of the 20g with 90- dergree Samco on it so I do feel that this restrictit somewhat but Harvey is 100% corect in the matter of different engines respond differently to the same mods.

Russell

ps - Before you say it, the tuner of his ECU is well known and that is NOT the issue!

 

I think bob's needs to stick a 20g on and see if it beats his 2005 times

I think it should but it would be interesting to see what he thinks of back road blasts with the 20g

 

We have had a 20G making 1.5 bar by 3400 rpm on a number of cars with no surge (Alans was one). On others you need to delay the boost building until higher rpm. My old RA was one of the worst for this......but then as a no compromise build it did go on to make 440.5 bhp on a 20G
There is a logical explanation for the surge related to the air speed at the turbo intake.
A std 16G or 18G will also surge if the set up isn't correct, as will VF34/35 on the later Sti's if you try and pull the boost in early without sorting out AVCS timing first !

Scoobboy, remember you are going to be running 95 octane. Most of the numbers quoted here are on 98 (and some also plus octane booster)

Andy

Russell, David was aware his old 2.0 engine was not in the best of health and was running retarded timing to preserve it, so not the best example of a 20G install. Jonnys and Harveys WRX's were tuned by the same guy btw

 

I found on my car with the same mods the 20G spooled slower than the 16G and was less responsive in lower gears. Makes sense since the compressor wheel is bigger and heavier. The following plot shows the best I could get out of both:



Both were on the same mods, both had no boost held back because of surge, and both had a whole bottle of NF per tank.

Whilst the full load curves show the 20G to be not far behind the 16G on spool, the on road response was notably poorer on the 20G, especially in 2nd gear for transients.

 

This is offset to a degree as the 20G wheel requires lower rpm to generate the same boost. Most of the inertia is the steel turbine wheel, not so much the light alloy compressor wheel.

John, I find the difference in spool is shown better if the x axis is time and not rpm.

 

We need to throw in compressor efficiency in the spool up area as well.

Interesting thread comparing Mg and alloy compressor wheels: http://www.lancerregister.com/showth...threadid=97279

Just plotted some x-axis with time for the same plots, I see what you mean!

 

last graphs are interesting , add in the recovery between gear change and I still feel the 16g is more suited to a non-sti rev limit.

andy,

do I recall , that when you added the forged(sti3 iirc) pistons in the RA , you did a bit of head work and stretched the rev limit to get the most from the 20g?.

I still feel the best example of a 20g was sg72's/your type r , that thing did not surge , had the revs for holding a gear during a back road thrash and went well as a whole package with the short gearing..... , the only issue was the limiter in top arriving almost unbelievably quick

 

Yes the RA had some head work done although I never changed the rev limit. Apparently the early heads are lower flowing than the phase 2's to start with ?
The type R cams help with the low rpm flow, eliminating surge in 95% of cases.
You need to try the 18G on my wrx now Still prefer the 04 hybrid though for backroad blasts

 

those graphs are for front entry 16g and 20g on a my99 setup, the cars i have worked on and my own went from 90 deg 16g to 90 deg 20g on pre 96and found improvements right across the board.

 

Interesting. On that basis if there are graphs to back up the 20G's improved low down torque with 90 degree entry, we should be considering fitting the 90 degree entry to our Phase II 20G cars or copying something else crucial off the Phase I engine?

 

there is no need to be a ***** cos i don't agree with you John, is there?

 

jonny,

was your car mapped/same mapper both times? .

I just can't work out why , with no other changes , how a larger heavier cold side can give improvements across the whole rev range and not just higher up. the 20g cold side will flow more but the hot side has to work harder to spin the bigger wheel in the first place which is why I feel a sti rev limit is more suitable for a 20g.

my thinking goes along the same lines for a flywheel here , on the same engine from a rolling start , a heavy flywheel will spin up slower but then give the engine an easier time than the light flywheel that spins up quicker but then the engine works harder to keep there. after a gear change the heavy spins with more momentum so does not drop as much while the lighter drops faster but again spins up harder. it is getting the balance right that makes the biggest improvement.

perhaps the 18g will be a nice in-between and it will be good to see how andy does with the 16/18/20g non sti tests.

the 1/4 mile probably is quite a good indicator as it will give indication to how the turbo spools of the line and recovers between shifts , the only thing it misses is the peak v rev limit for revving out.

as said earlier , the other good test would be bob's car with no other changes other than 20g. I would have tried it but I have just sold the 6speed , so the car will not be the same next year.

 

lol at jonny , it's called discussion

 

no my car wasn't mapped by the same mapper to be honest ( first time by rc developments and then andy) but Alan Bells car was mapped by andy both times.

 

no mate, that was sarcasm

 

I did not see it that way.

I read it as the 90* might let you bring the boost in harder without surge improving torque over a f/e

did alan bells car have a 6speed for both 16g and 20g?

iirc it was a UK car(?) with the 6speed , I did consider a 20g for a while after changing boxes as the shorter 1st,2nd,3rd,4th would help the 20g along but I decided the UK jump to 5th and 6th would still hinder things and the rev limit would need lifted too high.

 

I explained that above John, the 20G compressor wheel requires lower rpm to produce the same boost. The turbine wheel also produces greater torque at lower rpm (for the same exhaust flow)
In some (not all) cases a 20G or 18G can spool faster than a 16G. IIRC Andrew Carr also considers his new 18G spools faster than his old 16G

I mapped an Sti7 on an 18G last week and it was making 1.5 bar at 3050 rpm !

Andy

 

yes I understand that but is it not possible that the exhaust flow is slower through the hot side as the engine works harder to spin the 20g cold side , which it needs to make up first?. or possibly another thing may be if the 16g revs quicker the exhaust flow will be higher to a degree that the 20g just cant quite catch up on a non-sti?

edit. to try and make things clearer.

 

Exhaust flow through the turbine is relative to the backpressure, this is not directly related to turbine speed, more the exhaust housing and turbine wheel design.
The teensy td04 turbine will flow enough for 330bhp and during the spool phase we are only asking for circa 100bhp of flow through the TD05 turbine.

Having logged EGBP pre turbine on a number of set ups, it only starts to climb at higher rpm/loads.

 

fair enough .

do you have any 18g and 20g 1/4mile targets in mind?. iirc the 60foots at crail for the 16g where around 2secs but the cold day possibly balanced things out?

 

Not sure I will have it that long John, depends when Crail runs again ?? Looking at a MY06 2.5 early in the new year as a new project car and running through the same tuning stages as the 03 car.

 

cheatin booger

 

Needing an STi rev limit for the 05-06 20G is a falacy and I come to that conclusion from having driven a number of different cars, STi and WRX with the 20G. On my WRX Wagon I rarely go over 6250 rpm, even on the drag strip or in flat out driving.
Alan Bell's car had a 5 speed box when I first worked on it and Andy mapped it, more than once from memory as we did other things. It still had a 5 speed box when I fitted the 20G and Andy mapped that too. This was a particularly impressive setup compared to some, virutally no lag and instantaneous boost available on the right foot from 2500 rpm and full boost, 1.5 bar well before 3500 rpm. I don' t think it was as nice a car with the 6 speed and that was Alan's view too.

 

Something else I have just remembered that is significant: Following the success we had with Jonny's 90 degree and another similar car which was early in the evolution process, we came to the conclusion ie. Jonny, Andy and I, that straight in entry was not likely to show any great power gains over front entry and it became much less of a priority. Put another way I think we said the 90 degree entry was not costing the power drop we expected. It was also concluded that because of the 90 degree bend prior to the compressor turbine this was likely to have a beneficial effect avoiding compressor surge.

 

non sti 16g,18g v 20g shootout at scoobyshootout anyone

 

That is the sort of thing I was getting at Jonny. Would anything get in the way of getting the 90 degree angle in on a Phase II car? I'm sure T-uk might consider trying one?

Needing an STi rev limit, and appreciating one are two different things. Following Andy's prompt to show the graphs by time, I wouldn't consider a 20G on a 7000 RPM limit, the response at road legal speeds just wasn't there on my car until I had a 2.5 - then it felt like a TD04 on a 2.0, then I ruined it again by fitting bigger turbos. It is all preference.

 

not sure if the 90* clears the inlet manifold but if it does and it allows better all round performance gains as reported, not just an extra 40ish bhp at the top with less low down , that the car never makes up , other than at the very highest speeds , then it is worth considering. an extra 40ish bhp with no down sides

I think the 90* must bring things down lower if harvey , even on the strip feels no need to rev higher than 6250rpm. even with the 16g I was revving much higher in the lower gears , don't know where jb shifted at when he used my car?.

 

I try to work on changing gear when the power at the wheels in the next gear would be higher than it is from carrying on revving, or wherever the rev limiter is to protect the conrods/crank/valvetrain whichever is soonest. On the plots shown off my car that would be the rev limiter at 7000 RPM. If another setup was running more midrange torque it might actually gain from changing earlier?

 

I'll bring the 16g

 

New age WRX. Pump, injectors, decat, ported headers, sti tmic, panel filter, remap.

Red = TD05-16G Blue = TD05-18G



Ran a 12.8@111 on the 16G in a full weight 03WRX with a gentle 2.1 sec 60' I think the 18G may improve on that