I have an APS TT running 8psi on a stock block. I would like to increase the boost to around 14 psi but don't want to go all crazy on an engine rebuild.

Is changing the rods and pistons enough to achieve my goal?

 

i don't think anyone really knows whats the absolute minimum to run 14 PSI..

could be rods alone since the stock rods are real thin and are usually the first things to go... could be a headgasket that would make it cooler thus not making the rods go so fast..

i think once you decided to touch the internals of an engine.. its just best to do it all at once

 

I would go with rods, pistons and ARP hardware.

 

And a Cometic/cosworth or HKS head gasket will be needed.

 

Get those L19 studs. there are companies that sell complete short blocks that should suit you fine. that and get some upgraded actuators from Forge. And some bigger injectors. And a UTEC. And......well you get the idea. There have been a few that have gone this route. Do a search and find all the answers you need homie.

 

NO.

 

On the hardware side, you will need rods, pistons and good head studs. The other thing you need to investigate is fuel. Will the APS injectors and pump feed the beast at 14psi?

 

I need to put a limit somewhere otherwise the mods are going to get out of hand. I'd like to keep the APS TT kit as is (except maybe for the actuators). That is I do not want to change any part of the fuel system. If that means running lower boost than 14 psi, so be it. I would also like to keep the Unichip.

So what I need are upgraded pistons, rods, studs, head gasket?

Thanks for all the advice guys

 

You don´t need to replace the actuators , I´m in the limit of the aps fuel system with 450 rwhp, running 10.5 psi.
If you are thinking in 14 psi , you will need to replace all the aps fuel system ( complete fuel return, bigger injectors , and some kind of EMS to control new injectors size ) and off course ,an overboost controller.That means a lot of money...........

 

chances are the changes you will need are replacement of your hood when the stock motor jumps out of the car and hits it at 14 psi..lol
seriously, build the bottom end at least with a lower compression ratio and stronger rods and head studs, then a really good tune..

 

I am tuned to 11psi with the APS kit putting out 480whp, however that was on a dynotune. When i am out driving my boost levels spike to 14psi. Im in the middle of an engine build so until my work gets done i want to run a little strong and see what i can get out of this motor. I dont know how safe this is for a long term car though.

As of right now all i have is the cmplete aps kit, with the 3.5 inch exhaust and an ems.

All in all, after my engine build i am hoping to be able to run over 600whp with 22-25 psi. I realise this is an optimistic goal, but it would be wonderful to be able to get that type of power outta this kit!!

 

The standard APS TT kit is good for about 18psi, after that it looses its efficiency...

 

Yes, i thought about that. Which is why im probably going to switch the kit out with the extreme kit, or maybe just use the gt30's from the c6 kit that APS makes. Until then, guess ima have to be happy with where i am at.

 

I must have been a tad too optimistic with the stock APS fuel system. So the max boost I can run safely with the stock fuel system is only 10 PSI.

So considering the stock kit comes out with 8PSI, does an increase of 2 PSI really require changes to the engine internally or is a good tune and good fuel adequate.

Thanks again for all the replies.

 

You are kind of missing the jist of things.

To run 14 psi, you will need to build your lower end at a minimum.
Rods
Pistons
head and main studs

Usually this would include dropping your compression ratio - lower compression results in more boost being run and higher fuel demands.

This is what I have done:
Eagle Rods
Arias 8.8:1 CR pistons
ARP head and main studs
OEM head gaskets

I am running stock APS setup wtih upgraded actuators. I am running an 8.8:1 compression ratio and have basically maxed out the stock APS kit -> limited by the injectors and EMS. I peak at 14 psi around 4200 RPMS, but I cannot hold that PSI to redline due to lack of fuel. What this equates to is a large amount of TQ -> 480 ft/lbs and modest HP -> 450 HP. Just think about it like this: I am running the TQ of 14 lbs of boost, but the HP of 11 lbs of boost; on a 8.8:1 CR motor.

I am looking into setting up my car to run the full 14 lbs to redline. Basically my tuner feels this can be done with larger injectors, a utec/HKS F-con/unichip Q, and a retune. Of course you can go with a full return style fuel system with rails, but can get by without it IMHO at 14 psi. At 14 psi on a basic short block, no headwork or cams, you should see around 500-525 whp.

My dyno for reference:

 

Looks like 460 whp to me.

 

460 was the tune on Chi-town's 93 octane. We have 92 here in MN, so I was detuned a bit for the lower grade fuel

 

I see, detuned a little for 92 octane, makes total sense to me now.

 

Thanks for the input Zivman.

Based on the info given I have 2 choices.

1. Run at 14 PSI which requires me to build my engine (at a minimum pistons, rods, studs, gasket) & upgrade the fuel system

2. If I want to keep the stock APS kit as is, the stock fuel system limits me to roughly 10.5 PSI to redline. So even if i spend the money on the internals I'm still limited to a pretty modest power increase.

So the next question is can I run 10 PSI on a stock block long term with some kind of reliability? I know a few guys on this forum are running this.

 

10 psi can be done, but long term??? really depends on yoru definition of long term. I think it can be done, but driving styles, supporting parts like oil cooler, possibly meth injection, and most importantly the tune will be contributing factors to one's success. From reading the boards, it is the TQ that is ripping apart motors. The stock rods just cannot handle the TQ at thse boost levels. If your tuner tunes in such a way to keep TQ low and shoot for a very linear HP curve, I think you can have decent success at 10 lbs of boost.

With all that said, don't get greedy. at 8-9 psi you will already have a near 200 whp over stock HP levels.