998 turbo mod

[Turboflash]

Recently, I completed a turbo modification that consisted of changing out both compressor and turbine wheels with the goal of improving air flow/efficiency in a stock system.
My attitude going in to this project was this is an experiment on an occasional use toy. If it works, then great and I'll be pleased. If it doesn't, then I'll change it back to stock.
My qualification on whether or not it was successful was to evaluate pre and post track dyno HP. If dyno HP was higher after change (with no other changes) then turbo must be performing better. If not, then change was not beneficial.
Summary:
1. There is a gain. Stock wheels are not optimal.
2. Without divulging the exact details, the engine performs better with mod turbo.
3. Without divulging the exact HP numbers; let me just say I had to increase fuel pressure about 5-6 lbs to keep same AFR as before change (in cooler 53 degF air). Keep in mind, the air temp and humidity was much cooler and dryer on test before change. So, having to increase fuel pressure that much with much warmer and humid air in dyno after change only means there was more air going through engine which equals more HP. The engine is an air pump. More air volume = more HP (everything else being equal). (P.S. I know the track HP change).
The cost of change, to me, was conservative. Less than $1000.
Was it worth it? Depends on your perspective and expectations.
I

 

[guardrail]

Are you keeping the details secret because you plan on selling it as a kit at a later date?

 

[Turboflash]

Absolutely not.

 

[DooZ]

Recently, I completed a turbo modification that consisted of changing out both compressor and turbine wheels with the goal of improving air flow/efficiency in a stock system.
My attitude going in to this project was this is an experiment on an occasional use toy. If it works, then great and I'll be pleased. If it doesn't, then I'll change it back to stock.
My qualification on whether or not it was successful was to evaluate pre and post track dyno HP. If dyno HP was higher after change (with no other changes) then turbo must be performing better. If not, then change was not beneficial.
Summary:
1. There is a gain. Stock wheels are not optimal.
2. Without divulging the exact details, the engine performs better with mod turbo.
3. Without divulging the exact HP numbers; let me just say I had to increase fuel pressure about 5-6 lbs to keep same AFR as before change (in cooler 53 degF air). Keep in mind, the air temp and humidity was much cooler and dryer on test before change. So, having to increase fuel pressure that much with much warmer and humid air in dyno after change only means there was more air going through engine which equals more HP. The engine is an air pump. More air volume = more HP (everything else being equal). (P.S. I know the track HP change).
The cost of change, to me, was conservative. Less than $1000.
Was it worth it? Depends on your perspective and expectations.
I

So...I'm assuming it was a simple increase in fuel pressure for the dyno, but what are the thoughts on the existing tunes dealing with the better efficiency for trail use? New tunes?

 

[Turboflash]

There's more air so if the tune can't adjust for that, it will be lean. Not innocently so. I think it will be enough to be trouble.
I think it will push the closed-loop tunes to handle it too. I don't have any experience with closed-loop as far as how much they can adjust. Without any way to increase fuel flow on normal tunes (non-closed loop) I would say it will be trouble.

 

[earthling]

There's more air so if the tune can't adjust for that, it will be lean. Not innocently so. I think it will be enough to be trouble.
I think it will push the closed-loop tunes to handle it too. I don't have any experience with closed-loop as far as how much they can adjust. Without any way to increase fuel flow on normal tunes (non-closed loop) I would say it will be trouble.

The closed loop tune will try to adjust AFR based on what it is being told by the O2 sensor. This means maxing out the operating window of the injectors (max duty cycle). If there is not enough fuel pressure available or the injectors are too small, the system will run lean while the closed loop constantly tries to compensate but will never hit target AFR. Raising the fuel pressure should address the lean condition.

 

[Turboflash]

Yes, but for those who don't have closed loop, and don't have AFR data, and think/hope their current tune would be ok with this mod, I doubt it.
As you mention, I don't know much closed loop can compensate. Once injectors are maxed out and/or there's not enough fuel pressure available, closed loop can't help.
Without doing the math, I don't know how much more fuel is delivered with a 5-7 lb increase in fuel pressure. Also, keep in mind the Stage 4 PEFI tune is a 4-bar tune to begin with. Meaning base fuel pressure is 58 lbs.

 

[sideshowBob]

I have closed loop and with stock fuel pressure it maxes out at just under +25% compensation on the data log to try to meet the tunes AFR demands
I have had to raise my SW stock injector fuel pressure to @ 50 psi ,from the sock 42 psi, with my header tuned SW on the 300hp setting to keep AFRs safe.

 

[earthling]

Yes, but for those who don't have closed loop, and don't have AFR data, and think/hope their current tune would be ok with this mod, I doubt it.
As you mention, I don't know much closed loop can compensate. Once injectors are maxed out and/or there's not enough fuel pressure available, closed loop can't help.
Without doing the math, I don't know how much more fuel is delivered with a 5-7 lb increase in fuel pressure. Also, keep in mind the Stage 4 PEFI tune is a 4-bar tune to begin with. Meaning base fuel pressure is 58 lbs.

Do the injectors get changed out with PEFI stage 4?

 

[Turboflash]

No. The "kit" comes with a fixed 4-bar regulator (58 lb) and a 4-bar MAP sensor.
Based on my track dyno results, likely I might need to run about 63-64 psi static.

 

[Turboflash]

BTW- at 18 psi boost, that's about 82 psi fuel pressure. My understanding is:
a) my TD adjustable fpr can handle 100 psi
b) the stock injectors are ok up to about 85-90 psi. After that, larger injectors would be required.
Does make wonder how close to the edge I am with waste gate lock in, 25 psi boost, w 63-64 psi static = 88-89 psi on injectors?
So far so good. AFR was steady at low 12's on dyno; C16 fuel. No indication of fuel starvation. Good thing for C16, lol.
Post-dyno fiber optic camera inspection showed piston crowns happy and plugs looked good too.
Still can't run wfo for miles, lol.