Garrett Turbos

[Ross]

I used this spreadsheet to play with figures and dribble over them, during the many months of planning for my upgrade... figures were pretty close for when I was running the GT3071R on the 3B - perhaps a little on the high side - but by about 5%. I calculated efficiencies using the compressor map.

I was pretty excited about the idea that the ABY ignition with light headwork would have probably put these theoretica figures on par with real life... really is a top job by Paul

Guess now I need to go back to the K24 figures and see if I can hit the magic 3-0-0

[A80Avant]

i must say that i used those as well,but hadnt done my homework properly to see that to get there you must have ported head,possibly cams and at least 3inch exhaust!!! for the 3071R to reach those figures...

Thats why i will consider something bigger in the future,even from 3076R so that i can at least get the hp i would like.But in any case these are good to have

[PaulJ]

How does the GT3071R compare to the GT30R and the GT35 on say an RS2 with 3" exhaust as that is what I have fitted along with SCAT rods and aiming at 420hp
once i get a clutch that works

[Jamo]

I'm getting values of 555 bhp and 700 nm with the 3076 on the spread sheet, running slight higher boost than planned

Try as I might I can't get near Aronmatics2 torque figures for his shorter block stroker with the same turbo.

[Jamo]

3071.63 420 - 450
3076.82 500 - 525
3582.82 550 - 600+

There are other factors, head porting and exhaust are the two main ones.


Ross lol I know what you mean

[S2central.net]

Head porting, camshafts and exhaust are what primarily change VE...

Only other way to increase power without changing VE or anything else mechanical is air temperature... So bigger intercoolers, water injection all help. The mass of air being consumed is the limiting factor and the colder the better for knock prevention ==> maximum ignition settings. Funky fuels like E85 can help too, but I've not captured enough understanding of that to add it into the mix...

Less restrictive air filters and pipework also contribute to gains along the way - you ideally want zero pressure drop between ambient and compressor intake, and zero loss between compressor outlet and the throttle body... This is where more efficient and less restrictive ICs make the difference on the big turbo installs where huge volumes of compressed air are being ingested.

[A80Avant]

my mechanic had told me once that they had built an RS2 around 550hp but back then mechanical boost etc and extra injectors,and they had used the OEM filter box,without any filter inside!!! His words were that if you do that you will witness that the car is so faster that you'd think that when you ARE using the filter(even KN) it is like having having 3 people in the car!!

Now this is dangerous,and they the car for drag racing back then,but is it possible to use some kind of material that holds the bigger debri that might come into the filter,and be much less restrictive to the inlet?

Other than that,i was hoping for more hp(unless the dynos are S$^#*^$ ) and i do have Bigger intercooler+water injection.So my inlet temps are way low.It is a stupid thing i didnt port the head when i had the chance.As for cams,i wouldnt tamper with those anyway.So because i also like the sound of the exhaust,i may keep that as well,and see what gains i can have in the future.

[S2central.net]

PapVas - running without air filters is dangerous alright - OK on a drag strip maybe but big risk on the road...

Sounds to me like you are maybe being limited by the exhaust if you have nice cold air already. It would be worth trying a better exhaust before the time and hassle of porting the head or fiddling with camshafts...

[A80Avant]

Paul,
i have a 3inch downpipe, x2 105mm cats , 2 silencers of 76mm internal diameter and 70mm diameter(2.5inch) cat back tubes.So basically,having a 2.5inch straight mostly tubing,cannot be the only factor of my backpressure.Also just to give you an example,when i did the remap with erdal,top EGTs where on the 930-950C on the hotside and i was using Milltek catback of 3inch.I then switched to BN pipes catback with 2x60mm tubes,and i got more or less the same EGTs.I then switched to the cat back i have now,and EGTs are again the same.If i was having more backpressure because of my exhaust,it would have been producing quite a bit of rise on the EGTs,wouldnt it?
I believe that the RS2 EM is restrictive as well,and the .63AR also.

On the other hand i have heard of 4cyl engines producing 450+hp happily with this turbo which is why i wonder it hasnt had the same effect on mine.

In any case if i get the chance to dyno the car here as well,i will just to see what an independed dyno says,cause in Greece all are messed up cause they are looking for clients to tune their cars afterwards...

[gedu]

Well yes, in theory all back pressure raises EGT. In most cases however, ETG stays basically same with different exhausts, because the backpressure in EM and turbine housing is so much greater that whole backpressure isn't affected that much. Your EGT is so high because RS2 EM and that tiny turbine housing are so restrictive.

[A80Avant]

My EGT is good at the moment,because it is measured on the turbo hotside,not the beggining of the donwpipe,so it is more reliable.Nevertheless,this is the point i was trying to make.It is not due to the 2.5inch catback,but mainly the EM and turbo hotside.

[Bram]

Time to swap them with a Wagner EM and 0.82 it is then Papvas

[Jamo]

Backpressure isn't measured by EGT so how can the point be made?

All exhausts are not the same some are free flowing than others, a true good system would be 3" from downpipe to tail, no change in size, no change to twin pipes in the centre, no cat or high flow sports cat.

[A80Avant]

im not entirely sure that is correct jamo,as i have heard most tunners say that when the back pressure is higher,they get hotter exhaust gasses because of the increased effort for them to be disgarded.Otherwise how do they know that when they are tuning a car? Less backpressure would create less obstruction,and thus less temperatures.At least that is how i understand it.

[gedu]

well, backpressure vs. EGT is quite elementary. EM+turbinehousing volume is constant. When pressure rises, temperature rises with same multiplier (http://en.wikipedia.org/wiki/Ideal_gas_law). Sure, that equation doesn't take into account that exhaust gas is complex molecyles, pressures can be quite high, and volume isn't that large, but those are only modifiers to that basic law.