Topic: Bigger turbo, more aiflow but not more HP?!

[Ames Performance Tuning]

That is my understanding as well.  I am going through a similar process and will let you know if we discover anything else to check.  Vince did add some extra tuning to help exhaust (scavenging?) and that helped utilize the extra air flow in my case. 

[SKY888]

Outlet of the turbo you mean right after turbine outlet (downpipe)? Or compressor outlet?

Kelu, I think DDM dave was referring to the pressure difference between the turbo compressor  and intake manifold.

im hoping that the Dejon IC that you have is not causing too much pressure drop.    But I really doubt that the IC is causing your issues right now.


have you checked the turbo's back pressure?

[Dave@DDMworks]

The case:

Stock turbo + catless downpipe + Solo Mach Cat-Back + IC ... airflow maxed around 31-32 lbs/min ... dyno estimated 312hp (in two sessions one year apart)

Big turbo + Garret casted exhaust manifold + custom catless downpipe + same cat-back + same IC ... airflow 40-42 lbs/min ... dyno estimated only 320-330 hp
Bumped the octane of the gas ... increased the timing from 12 up to 15-16 degrees advance .... dyno estimated 350-360hp

Dyno was same in all cases, almost same conditions, AFR pretty same, a little bit leaner with big turbo tho

Those values with big turbo would scream 400hp based on my estimations and I though dyno is bugged, took it to a drag race on a track where I raced many times and it confirmed that the power is correct, dropped only 0.2-0.3s from my stock turbo runs.

I don't get it, not sure what is happening, those values are normal? If is getting so much air, why is not producing power even AFR is leaner and timing same or more?

PS. I have data to back this up if is the case.

I was looking back through some of our logs and comparing them to what you posted and our 2871's are getting that same airflow of 40-42# with around the same timing and seeing around the same horsepower that you are seeing of 350-360hp at the wheels, so your dyno's do not seem that far off really.

[Kelu]

Dave: my dyno shows ESTIMATED at the flywheel, in the second dyno there is a small plot at bottom which describes the drivetrain loss somewhere between 30-70 hp lose which means 300-320 whp maximum.
With stock turbo, tune and catless exhaust same dyno I was doing 312hp - 278whp.

I didn't had the chance to dyno on this when I was bone stock, but this dyno is very good on stock cars with power estimated at flywheel, I have seen hundreds of sheet with stock cars and it does approach very good.

This turbo is still way bigger than a GT2871, should produce 400hp easily.

Kelu, I think DDM dave was referring to the pressure difference between the turbo compressor  and intake manifold.

The pressure is measured in intake manifold, even if I had a leak between turbo and intake manifold it wouldn't matter.

have you checked the turbo's back pressure?

Not yet, this is first thing which we will do when will have a normal weather.

[LatinVenom]

But is it not air flow the measure of power. Your big turbo is just putting out the same as the DDM 2871, so unless you can produce more air flow, I think the numbers you have are it with your tune.

[elff]

What about MAF vs the VE values you are seeing?
Should they be closer?

[Kelu]

My tuner ordered a bigger turbine housing from COMP, I had 0.64 IIRC and I think he ordered .82

Also his ECU Tuner (not the greek one) will come to Romania next month and he will have a look on my car.

[SKY888]

My tuner ordered a bigger turbine housing from COMP, I had 0.64 IIRC and I think he ordered .82

Also his ECU Tuner (not the greek one) will come to Romania next month and he will have a look on my car.

hmmmmm...you'll get more lag on that set-up though.

when I had the gt3582r, I had the .63  turbine AR.    And it's already laggy for me.    I can't imagine how laggier it will become if I had that .83 turbine AR.


But I'm hoping that this bigger AR will give you more powah!!!   Plus of course less back pressure will be produced with this bigger AR.

good luck with the tuning!

have you guys checked your Back Pressure of your current set-up?

[Arabas]

will you be keeping the old comp turbo, just in case you want to go again with that one?

[Kelu]

Arabas: I still have the comp turbo on my engine, I just replace the turbine housing.

Antonio: my turbo is way bigger than GT35, it can produce at least 700hp

[SKY888]

Antonio: my turbo is way bigger than GT35, it can produce at least 700hp

im not saying gt35 is bigger.

Im saying, your turbo will be laggier for upgrading from .64 AR to .83 AR turbine AR.   Your turbo is already bigger than a gt35....probably its comparable to a gt37 or something.   So definitely it will be laggy for a 2 liter engine.


lets just hope that the .83 AR will help out free up some horses.

so your comp turbo that "can produce at least 700hp".....will now produce more than what you currently have at the moment.

[SKY888]

Kelu....do you have the dimensions of your COMP turbo?

if you're stating that turbo can produce at least 700hp....don't you think, its TOO big for your 2 liter engine?


I'm looking at the garrett website, and saw that the GT4708r is a big turbo that can at least produce 700hp.



SPECS:

Compressor
Inducer wheel diameter - 79.8mm
Exducer wheel diameter - 108

Turbine
Wheel diameter - 92.7mm


recommended for 2.5 - 10 liter engines.

[Kelu]

I don't have the dimensions for my turbo, IIRC is a 6767 not sure which series. I could find it in CT4 and CT43 series:
http://www.compturbo.com/products/ct4billet/ct4_6767

http://www.compturbo.com/products/ct43billet/ct43_6767

"CT4-6767 - 975 HP" 

If is so, it is amazing to have 1.5 bar at 4500rpm with no update tune on a stock engine 

[SKY888]

both the CT4  and CT43 have:
67mm inducer (Compressor)
67mm exducer (turbine)

I guess it's comparable to a turbo in between GT3582r and GT3776.   

GT3582r specs
61mm inducer (compressor)
68mm exducer (turbine)

[Kelu]

In dimensions yes, in power delivery no )

[SKY888]

In dimensions yes, in power delivery no )

what do you mean?

[Kelu]

COMP CT4 6767 is capable of 975hp.

From Garret only GT42 is capable of over 850hp

[SKY888]

COMP CT4 6767 is capable of 975hp.

From Garret only GT42 is capable of over 850hp

oh gotcha!!!

i guess, its because the way they match their compressor and turbine wheels!

the COMP turbos tend to have bigger compressor inducer wheels..........compared to a similar sized turbo of garretts.

[Kelu]

have you guys checked your Back Pressure of your current set-up?

Nope

[Kelu]

New update

Tonight car was dropped off to the garage.

The COMP send a new turbine housing, .82 AR instead of .64 as I had before because they said my 7676 triple ball bearing turbo is choking with a huge compressor capable of 800-900hp and such a small turbine housing. I hope it will not lag way too much with this new turbine housing.

Also the ECU tuner will make the remap on dyno for it. Also he said that the placement of the external waste gate was bad and they might have to remake the downpipe.

The good news is that my local greek tuner didn't replaced the dyno yet and we will have same baseline.

We shall see in a couple of days.

[elff]

Sweet
Keep us informed of the progress

[shabby]

The COMP send a new turbine housing, .82 AR instead of .64 as I had before because they said my 7676 triple ball bearing turbo is choking with a huge compressor capable of 800-900hp and such a small turbine housing. I hope it will not lag way too much with this new turbine housing.

Unless your current turbine is smaller than the stock turbo's one you're not choking it at all, perhaps if you were near that 800-900hp level then sure, but not at the current level. There will be more lag with a bigger turbine. I still can't find any specs on that turbo, got a link to them?

[Kelu]

Sure: http://www.compturbo.com/products/ct4billet/ct4_6767

[miller11386]

Kelu you will spool up to 30lbs around 5500rpm

From what I have seen on my turbo (on other 2.0L engines) the  3586 spools up around 4500rpm, 6262 is around 5300rpm and by extrapolation the 7676 would be around 5500rpm to make 30psi (not sure if you are planning to push out 30psi or not)

However she wont quit pulling... get the valve train all spec'd to roll to 8k rpms and beyond. That is the magic of the 2.0... when putting a big turbo on and spinning it up high it just keeps making more power. Your dyno graphs turn into mountains.

Goodluck, and i think its a good move to go the .82 A/R housing... .64 is too small for a 2.0L IMO

[Kelu]

Kelu you will spool up to 30lbs around 5500rpm

What is that? Airflow?

From what I have seen on my turbo (on other 2.0L engines) the  3586 spools up around 4500rpm, 6262 is around 5300rpm and by extrapolation the 7676 would be around 5500rpm to make 30psi (not sure if you are planning to push out 30psi or not)

Miller your words sound nice but ...

This turbo made on my stock engine 1 bar = 15psi at 3200-3500rpm
And 1.5-1.7 bar ~ 25-25psi at 4300-4500rpm

However she wont quit pulling... get the valve train all spec'd to roll to 8k rpms and beyond. That is the magic of the 2.0... when putting a big turbo on and spinning it up high it just keeps making more power. Your dyno graphs turn into mountains.

I prefer mountains of the HP plot at the end of rpm
Instead of high mountains of tq at low rpm