Am I correct that in order to increase the boost beyond about 10psi on an APS TT that I need to replace the actuators?

Are the Forged offerings the way to go?

What boost range would one target with cams, minor headwork, and a stout bottom end?

Thanks in advance.

 

Boost controller....

 

^^^^ +1

Also, you need to find out what turbos they are. APS use to use Garrett, but years ago I heard they changed. If you have Garrett's, find out the P/N, then you can look up the compressor map for the compressors on your turbos on the Garrett site. Garrett provides a tutorial on how to apply the compressor map to your engine displacement. Even more easy, I can send you the spreadsheet I use. It is pretty good at predicting fuel flow and boost pressure for a desired hp (assuming supporting modifications are in place).

Whether you get new cams depends on your goals. Most people with a built motor do. I match ported my heads, but the benefits are minor. VQ heads are actually quite good stock. Nonetheless, if you already have the engine apart, it wouldn't hurt.

You can go as deep into the build as you want, but it all costs $$$. I would search the FI forum for builds other people have put together, look at their results, and get an idea of what you want.

 

Also, if you are getting new cams, check to see if they require new valve springs. Some cams do. I also replaced my stock valves with Ferrea valves. I don't remember where the limits of stock valves are when using high lift cams and aftermarket springs, but if you are already going that far, it probably would be prudent to put in stronger valves.

 

I have the JWT C2 cams and the recommended JWT valve springs to match.

Here's a link to the long block: http://www.importpartspro.com/st2vqloblni3.html

The Haltech PnP has a built in boost controller.

The turbo kit was installed by the original owner back in 2004, so is it safe assume they are the Garrett units?

I'd love to see your spreadsheet. Can you email it to mylesridesbikes@gmail.com?

Thanks for all of the advice.

 

To answer the OP's post correctly:

If you have the standard APS with internal wastegates, you can see about 12 psi by adjusting the tension of the rod. Beyond that you will need a stronger actuator. If my memory serves me correct the Forge actuators worked great and were rebuild able, but very pricey. Im sure if you contact Garrett turbo you can order stronger actuators.

With the Forged actuators (that have nothing to do with Forged Performance in GA) I was able to achieve 18 psi, but that was about the efficient limit of those turbos...

If your replacing the cams with anything more aggressive than a Nismo, you need to do springs. At that point you might as well dig into the heads.

Hope this helps.

 

Sent

 

I have the same problem, APS TT Garett turbos and 10-11psi max even with boost controller at 100% duty.

Need the forge actuators so I can get 16-17PSI.

 

Do your turbos have an internal wastegate? If so, you may want to add an external wastegate. Before doing anything, however, find out what compressor is on your turbos and check the compressor map to make sure the turbos will give you the boost and airflow you are looking for without going beyond the choke line. Some guys do run beyond the choke line a little bit, but the turbos are very inefficient in this range and the compressed air is hotter than normal, in which case you want a large and efficient intercooler.

The following link describes compressor maps:

https://www.turbobygarrett.com/turbo...ompressor_maps

In the spreadsheet I sent, Manifold Absolute Pressure is the amount of "boost." The pressure ratio is the value you use for the Garrett compressor maps.

 

depends on your exhaust, but forge with blue springs would be a good general setup. I run the reds on APS 2.5" exhaust. spring pressure is about 12.5-13... when cold it will spike to about 15. I generally just keep my boost controller off and run spring pressure.

my good buddy put the blues on his setup (which is basically the same as mine except BC cams vs my GTM cams) His boost was a little more controllable. he used his boost controller to dial it in. where as like I said with mine, I mainly run with it off.

15-16 psi makes for a pretty fast/fun setup... heck, 12-13 is pretty fun

 

Here's the spec on the turbos directly from APS:

"The turbos are Garrett GT2535R Water-Cooled Ball-Bearing Turbochargers
It is a new hybrid specced by APS for Garrett to produce to match the VQ35DE. What the alphanumeric name means is, the turbine side uses the GT25 housing and the compressor uses a GT35 housing. They have changed the model terminology and are now referred to as GT 2871R."

Given that this is a "hybrid" setup, I don't know what compressor map to reference (or how to read it!).

I don't want to buy more parts than I need, but will certainly invest in what makes sense.

Can I just get the Forged actuators and trust the tuner to raise boost until the limits of the existing hardware are reached? Would an experienced tuner be able to tell from the data when the turbos have reached their limits?

My understanding is that the APS kit uses an internal waste gate. If I upgrade to an external unit, is the internal unit removed? Bypassed? How does this work?

Thanks again for everyone's input.

 

Exhaust:

APS 3.0” Stainless Steel “True Dual” Exhaust system
APS 3.5” Stainless Steel Test Pipes direct to Turbo outlets

If your boost is less stable, wouldn't that be less safe for the engine? With a Haltech PnP, could a tuner keep a firm grip on boost pressure or is something more mechanical in nature outside of the EMS?

Thanks!

 

what I'm saying is that the reds are the strongest springs you can buy. they are influenced a lot by outside temps. In the summer when it's 75+ that's not an issue. ~12 psi on spring pressure. Use my boost controller to dial into 15-15.5. but if temps drop to 50 degrees, now I'll see 15 lbs on spring pressure.

If I ran the blues, my spring pressure might fluctuate 9 psi to 12 psi... in that case, could use my boost controller all the time and run 15 lbs and let it do the work to keep my boost levels more stable.

I'm running the reds because I run the 2.5" exhaust. after seeing what I had going, my local buddy chose to use the blues. On a 3" exhaust, I would think the blues would be plenty

 

this is a 25/35 hybrid.. the GT2871RS turbo comes to my mind, though, it's been yrs since I have talked this specific about the setup. forget using an external. with forge actuators you will do just fine. from what I know/have seen, these turbos run out of steam at about 18 psi... they will still flow up to 20-21 lbs, but lose efficiency and start blowing hot air. I think one person has cracked 600 whp with them. I would shoot for 15-18 psi. 18 psi is a lot of boost on a N/A motor like the VQ. Shoot for a solid tune mid to upper 500's whether that is 15, 16, or 17 psi. don't get hung up on the boost pressure. make sure the car is tune well, drives well long before you worry about the max power it's making.

Like I've said, I just run spring pressure 95% of the time. whatever you would make at 12 psi will be more than enough for the streets

 

Did you even rad my post? I did all this and went through all this back in 2004. All you need to do is what I said...I did all the hard work so you don't have too.

 

Yes, you can use actuators with your internal wastegates to control your boost, but you still need a boost controller to control the actuators.

My understanding is that the internal wastegates do not work well with high boost applications. In fact, some vendors who use the internal wastegated housing (because it fits with a t25 flange on the log style manifold) actually weld the control arm to keep the internal wastegate closed, and instead provide an external wastegate. Tial is a popular one to use.

APS used to offer both a base turbo kit and an extreme turbo kit. I *think* the GT2871R was used on the APS Extreme turbo kit, not the base kit. Is yours the base or the extreme? The Extreme kit came with a fuel return system. If I remember correctly, yours did not, which may indicate that it is not the Extreme kit. Anyway, the GT25 and GT28 turbines are not the same, so I am not sure how they correlate the GT25 turbine with the GT2871R turbo. Maybe they machined out a GT25 housing to fit a GT28 turbine, which may be the case.

That being said, if you have a GT25 turbine housing, it may be a little restrictive if you try to obtain high boost levels (say over 16 psi of boost). I have that issue with my GT3071R (0.64 A/R) turbine housings (on a 4.0L motor), and very soon will be replacing them with 0.86 A/R housings. Based on Garrett's GT2560R turbine map, the GT25 turbine housing also is 0.64 A/R and appears to be more restrictive than my current GT30 (0.64 A/R) turbine housings.

 

If by chance you do have the 71 mm compressor, here is a map from one of the four GT2871R turbos listed on Garrett's website:

 

Also, the GT2871R (3) is available with a 0.86 A/R, which will be fine. Many of the GT2871 turbos, however, have 0.64 A/R. If you have a 0.64 A/R housing, torque will drop in the high rpm range, but the torque will come on fast.

 

The Base APS TT kit turbos GT25 housings with GT28 hot side if I recall correctly, they stopped being efficient at 18 psi on race gas for me. I was making 24 psi on the upgraded extreme kit with external wastegates.

 

Sounds like a set of Forged actuators, the Haltech boost solenoid, and we'll see what magic happens.

This has been quite a learning curve for me so far - and I still know squat. Thanks for bearing with the newbie questions. The explanations offered have been very helpful and informative.

I'll keep you guys posted on results.