Which turbo for Q4?

[nick]

hi guys
my q4 has got garrett t3/t4 turbo
i want to change turbo but i have not an idea
I want to fill the turbo at low rpms...
gt28 for this appropriate?
or what do you recommend?
now its filling 3500-4000 rpms..
low rpms likes death
and one day ago we changed headers..

[jimnielsen]

Is it a racecar or a street car?

[nick]

hi jimni..
its street car not race

[Steve Webb]

Hi nick, what other modifications have got done to the engine? I've got a t3/4 and tubular manifold as well and get plenty of boost low down.

What exhaust have you got?

Are you running with a standard ecu \ chip?

[nick]

hi steve.
well the specs are below
garrett t3/t4 turbo
walbro fuel pump
magnecor kv85 spark plugs cable and ngk b8egv spark plugs
chipped by maxiboost
and tubular manifold
and complete exhaust 60 mm with not cat..

[Steve Webb]

hi steve.
well the specs are below
garrett t3/t4 turbo
walbro fuel pump
magnecor kv85 spark plugs cable and ngk b8egv spark plugs
chipped by maxiboost
and tubular manifold
and complete exhaust 60 mm with not cat..

Personally I'd look at the exhaust first, 60mm is a little small. 63mm (2.5") is pretty much the minimum size once you start modifying things.

How many silencers do you have? You only really need the 1 at the rear of the car.

[Brul(tm)]

I have a 3" exhaust from the two kats all the way to the back, only one silencer. The smallest they had where the exhaust was fabricated.




I also had remove the first small kat rigth after the down pipe.
The kick from the turbo came around 2800RPM instead of 3500 RPM.
I still have the original exhaust manifold but with an Delta Evo spec original turbo

Regards,
Marc

[Steve Webb]

Any excuse and you are showing off your big fat pipe eh Marc?

[nick]

I have a 3" exhaust from the two kats all the way to the back, only one silencer. The smallest they had where the exhaust was fabricated.




I also had remove the first small kat rigth after the down pipe.
The kick from the turbo came around 2800RPM instead of 3500 RPM.
I still have the original exhaust manifold but with an Delta Evo spec original turbo

Regards,
Marc

i dont think
0,3 mm doesnt matter..

[Steve Webb]

Hi Nick,

that extra 3mm diameter works out as a 10% increase in cross-sectional area of the exhaust.

As for Marcs 3"/75mm system, that has 56% more CSA.

To spin up the turbo you need a pressure difference between the input and outlet to the turbine. Reducing the exhaust back pressure obviously helps achieve an increasein this pressure differential without increasing the pressure going into the turbine.

Only my opinion, but if you do splash out on a newer style of turbo, you might end up being disappointed with it as it is still being limited by the exhaust.

[Brul(tm)]

This helps a lot


Regards,
Marc

[Steve Webb]

That really is a free flowing silencer box isn't it?

[Xti]

Hi, guys...
I also intend to change the original turbo, maybe with a GT28RS.

I already have changed the exhaust with a 65mm one (no cats at all just the rear silencer). Do you think that might in some sort of way have a negative impact on the backpressure or flow of the ex gases? Thank you!

Cheers,
Cristian.

[Steve Webb]

Hi Cristian, I ran with a very similar exhaust to yours for a while, and managed to make 270bhp with it. Although the power tailed off very early, from 5000rpm.

You will probably notice a difference with a new turbo, but it might not work to its maximum.

What other mods has your car got?

Thinking about it, this is the perfect example of why the forum garage can be so useful. If you have entered all of the details about your car into the garage, we can just click through to there and see exactly what you are running, and give you the best answer.

[Xti]

Hi Cristian, I ran with a very similar exhaust to yours for a while, and managed to make 270bhp with it. Although the power tailed off very early, from 5000rpm.

You will probably notice a difference with a new turbo, but it might not work to its maximum.

What other mods has your car got?

Thinking about it, this is the perfect example of why the forum garage can be so useful. If you have entered all of the details about your car into the garage, we can just click through to there and see exactly what you are running, and give you the best answer.

Pretty much all the mods I have on my Q4 now are:
- this 65mm decat and straight to the back exhaust with a DTM style finish for the rear silencer;
- D2 Street Kit coilovers with Eibach springs at the back;
- kevlar reinforced OEM clutch (local workshop job but it bites quite well...so far);
- some silicon pipes for oil/water and a Samco one for the inlet manifold
- EGR removed;

Still to mount...
- Hormann strutbar for engine (coils kit bolts are too short and needs some adjustments);
- bigger FMIC (it has diagonal flow but I'd like to change that first) but I'm thinking that would mean also bigger LAG without an appropriate turbo;
- Turbo pressure gauge (not connected yet);

Very few mods but I'm glad I've made it to an end with this 3years rebuild project which took me lots of time, energy and money. As we're expecting the 3rd baby to be born and also struggling with these days financial difficulties here, my Q4 seems to be catching my wifes "attention" more than ever before... if you know what I mean. I will think to a price just to keep the peace around but I realy think the buyers will keep themselves far away...

I will try soon to find the time to present my Q4 into the garage.
Cheers guys,
C.

[Steve Webb]

Hi Cristian,

not sure how others feel about this, but unless your current turbo is about to die on you, I'd probably look at other places under the bonnet to start improving things.

Personally I'd look at getting a tubular manifold to improve flow into the turbo first. Then maybe look at replacing the standard airbox with a cone filter or something similar.

Anyone else got any ideas?

[Xti]

The OEM turbo doesn't seem to fail yet even I've noticed some minor axial play when cheched before mount it to the engine.

I also have a T3/T4 turbo for spare but it's pretty big and I assume I would have to make some more space if I'd want to have it on (but that wouldn't be such a problem...). The previous owner of this Q4 said he has got this hybrid tb from States (SS Autochrome) but I didn't found any "label"on it and first I have thought it must be some cheep chinese turbo. He also said that tb has only covered 2k km. It was mounted with an external XS Power WG but I also found some unsatisfying reviews about. Do you by any chance heard the same?

Yes, the very next upgrade has to be the tubular manifold. Besides that, the FMIC.

I already have a Sparco sport air filter which is located on the original box, don't know if I want to change it for a con air filter due to pretty dusty environment we have around here. But I like the idea. BMC CDA maybe...
I realy appreciate your suggestions and all the others that might come.

Cheers,
Cristian.

[Steve Webb]

Were the bad reviews you heard, about the turbo or the external wastegate?

When I swapped over to the T3/4 I was more than happy with it. Although I was coming from a standard T3 that had failing seals. On the overrun the car way laying a smoke screen that a WW2 destroyer would have been proud of.

Personally I'd get hold of a cheap tubular manifold and stick it on the car with the T3/4.

[Brul(tm)]

laying a smoke screen that a WW2 destroyer would have been proud of.

By any change got some film of that


About replacing the air filter. I think you will get better results in providing enough cold air. As we all know, it gets quite HOT under the bonnet....
Just replacing the original airbox won't help you, it just for the sound of it

Regards,
Marc

[Xti]

Were the bad reviews you heard, about the turbo or the external wastegate?

When I swapped over to the T3/4 I was more than happy with it. Although I was coming from a standard T3 that had failing seals. On the overrun the car way laying a smoke screen that a WW2 destroyer would have been proud of.

Personally I'd get hold of a cheap tubular manifold and stick it on the car with the T3/4.

The bad reviews (not for the T3/T4 but just for the WG) as I remember were from a site in the US, there was a guy saying that his XS Power WG failed instantly causing damages to the tb, other one was saying that there are better options reagrding WGs than XS Power, etc...

Anyway I think it wouldn't be a problem for me using it. And I'm seriously thinking at a tubular manifold.

Yes, Marc... your point is correct as it is indeed very hot under the hood. There are some compromises that must be done and colder air is needed for more power.

Cheers,
Cristian.

[Brul(tm)]

There are some compromises that must be done and colder air is needed for more power.

During the winter time, take it for a spin.... you will feel the differance!
I always did, it's huge....

Regards,
Marc

[Steve Webb]

By any change got some film of that

Sorry no pics, but just imagine a large grey rain cloud appearing from the rear of the car when you lift off the throttle and you are just about there.

[wrinx]

This was mine, which made a huge smoke screen when driving:



wrinx

[Steve Webb]

Whoa!!! that was like some sort of hypnotism with the camera focusing back and forth!

Strangely mine didn't smoke much when ticking over, only on the overrun. I hope you used a good quality oil, makes the smell of that so much nicer.

[nick]

hi guys
i have canceled change turbo charger..
t3/t4 is keep going
and today the engine has started then tubular manifold..
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