artos

At this moment I'm driving an STI MY 03/04 with GT-Spec headers, bigger fuelpump, ported VF35, Invidia 3" and Ecutek (EMS). In the near future I'd like to buy a 2.5 L USDM Shortblock. My goal is to stay below 400 BHP, let's say around 380 BHP, keeping internals and internal wastegate, maybe bigger injectors (650 cc.) I'm searching for a turbo that is absolutely free from boostcreep on a 2.5 L. in any gear at any revs. A VF35 is not free from boostcreep on a 2.5 L. Maybe a VF34 will do, but that one is maybe a littlebit too small, and only capable of 360 BHP(?). I've been reading a lot lately on the forums and saw many opinions on the TD05/06 18G, 20G, but also about GT30R (-10, -11,-12). But I never was convinced that they were absolutely free from boostcreep. So I like your opinion from all the turboguru's, is there any turbo available which matches these specifications?

Arjan.

john banks

My iON P450 which is a GT30R with a P20 housing for bolt on, creeps to about 0.9 bar.

TD05-20G with ported wastegate crept to 1.2 bar.

Neither give any surge.

Both of these turbos have more substantial compressor sides than turbine sides, which will encourage boost creep, limit power but give possibly better spool up.

I don't know what is guaranteed to give no creep except perhaps you need a decent sized external wastegate, Tial 38mm has been known to still creep, Tial 44mm apparently OK.

But a bit of creep below your target boost should not be a problem?

dowser

Larger wastegate penny? What was the URL for the US site that sold these?

I ported my wastegate on the 05/06 to the max possible on the stock penny. On an EJ20 it saw creep max of 1.2 bar and no surge. Then changing the headers for less restrictive items moved this to 1.3 bar of creep and surge below 4k at anything more than ~1.4 bar.

Richard

R19KET

Fitting a bigger WG button allows the WG to be ported out further, and creep can almost be eliminated on the TD05/6. On the P18/P20's, it can be ported with no creep. It's a lot of work though.

One of the biggest problems with External wastegates, is controlling them as they were designed to be used.

Most people don't have an ECU capable of applying pressure to both sides of the WG, which allows a very weak spring to be used. Consequently, stronger springs are fitted to aid spool up, but this can cause creep issues.

The 38mm Tial, and similar, have been used to circa 600bhp without problem. The 42mm Turbonetics "Racegate" is rated to 900bhp.

Mark.



Mark.

artos

"But a bit of creep below your target boost should not be a problem?"


That's a bit difficult to answer for me, because I'm not that technical and I'm from Holland, so I don't understand all the technical words. But does it mean you set your boost lower, you also loose some BHP? I don't think that's what I want.

What do you mean by 'surge', is it the same as 'spike'? Which means, when that happens, you're in trouble?

Arjan.

Thanks for your answers anyway.

XNWRX

Just a question : why are you looking for a USDM 2.5L ? Your 2.0L is as reliable as the USDM2.5L for 380 bhp. It might even be more reliable.
TD05/06-20G from Andy doesn't creep at all on a 2L engine (0.6 bar). Anyway, looking for about 380bhp will require 1.35 bar at high rev on a 2.0L engine and about 1.2 bar at high rev on the 2.5L engine...so why to worry about boost creep ?
boost surge occurs when exhaust gaz are not sufficient to make the turbo built the requested boost...so at low rev, it corresponds to the maximum boost you can acheive.

Richard, you worry me...I currently have no surge at all, with 1.6 bar @ 3600RPM...and I'm going to fit my new PowerStation header/uppipe next week... !

dowser

I went from the Maxim design to an iON one - I guess the PS one will be closer to the Maxim? Your inlet path will also be a factor - I'm running an MRT inlet pipe with a K&N cone.

Richard

artos

"Just a question : why are you looking for a USDM 2.5L ? "

Because I like torque down below, on a 2.5 L. your turbo will kick in at about 2600/2700 RPM, with a VF34. I drove in a 2.0 L. STI with TD05/06 20G and the turbo will kick at only 3300/3400 RPM, in my opinion that's too late. In my own STI with VF35 it kicks in at 3000 RPM. I don't want to give up the spoolup around 3000 RPM.

Arjan.

XNWRX

I will let you know about the PS header Richard. Inlet is based on modified Perrin hose and stock airbox (and some other mods)...seems to be OK.

Good reason Arjan. Then you should look for a 2L twin-scroll JDM engine as well. But the TD05/06-20G on my 2L STi7 built 1 bar @ 3100RPM...not so bad for about 400bhp. That is usable range extends from 3500 up to 7000.

john banks

The twin scroll from the Type 25 could be nice on the 2.0 also? But by the time you've got it you might have been cheaper to buy a 2.5?

I get the same (but not more) out of my iON P450 on Optimax as I did out of the 20G with methanol or NF. I do lose out on about 400 RPM of spool on the iON compared with the 20G for the torque to come in in 4th gear, 1 bar point is 300 RPM later in top gear - 2450-2500 vs 2750-2800 for 20G vs iON. The 20G on the 2.5 had no real lag over 3000 RPM. It was nearly impossible in normal driving to be caught without boost available very quickly. With the same heads and turbo the 2.5s do peak earlier than the 2.0s giving less of an advantage than you might think if you can rev the 2.0 to 8000 RPM or higher. The 20G is a lot nicer on the 2.0 with 8000 RPM vs 7000 RPM limit.

dowser

And that's the point you need to be careful with using the 2.5; it's all well and good having 1 bar of boost at 2k5 on a vf34, but no bloody good at all when the exhaust wheel becomes the same restriction as the td04 on a 2.0 above 5k

Still, if your target is around 380 then it should be achievable without too much back pressure.

Richard

artos

So, last question to John Banks:

You think it's safe then to go for the 2.5 L. with TD05/06 20G and bigger injectors?

Thanks for your opinion.

Arjan.

john banks

You can only try it, get the wastegate ported to the max and if that doesn't work change the penny to a larger one.

PICKLE

Right let me be really thick! How would you describe what boost 'creep' is, and how can I tell if my car is suffering from it?? Sorry but this is one thing I don't understand, and I hear alot about.

Cheers, James

ASTiMAN

I'm running the TD05/06 20g on a high spec 2.33litre and seem to get overboost (boost creep?) on part throttle acceleration and also lift off from full throttle. Max boost at present is set at 1.5bar (22psi). I have Gruppe-S headers and full 3 inch system, using a Link ECU and 3 port boost solenoid. Any ideas what would cause this and suggestions for cure would be greatly appreciated.
Apart from that spool up is incredible and it is very difficult to drive off boost!

Kind regards
Andrew

dowser

Boost creep: your wastegate cannot pass enough gas, even with the actuator fully opening the wastegate. Therefore, as revs rise so does boost. To see if you're suffering, simply connect a hose between turbo outlet and wastegate, and monitor boost through the rev range to redline. If boost slowly 'creeps' up, your wastegate is restricting flow (standard wastegates should open at around .7 bar, and maintain this boost to the redline [in most cases....]).

Astiman - sounds like your boost control maps need some work

Richard