PowerFC Turbo/Injector Downgrade Question

[hstylez]

S14 SR which is currently tuned with a PowerFC D-Jetro (map sensor)for this setup:
GT2871R .86AR
850cc Injectors
Megan SS manifold

I'm switching to the following setup:
S15 Turbo
525cc Injectors (STI)
Stock Manifold

Obviously I will need a tune for this to run well after all the changes. My question is: do you think I can get the car running well enough to drive it(out of boost) to a tuner 100 miles away? If so, what values in the PowerFC can I adjust to correct the injector difference since that is my main concern.


7/6/12 Update: To anyone who ends up searching for this and is curious of the result, the injector scaling worked perfectly and the car runs fine. Simply all I did was scale the injectors based on the new size. New size is 525cc, stock is 370cc. Divide 370 by 525 and you get ~71%. That is the value I used on the PowerFC and the car is running great. Heading to the tuner this weekend for fine tuning.

[Croustibat]

You can, but this requires a wideband lambda sensor. You could just try multiplying injection time by 2, it will be safe. They may have similar latency, but if it bogs down on idle try changing the latency to a lower value.

I dont know how you do that on a powerFc though.

[hstylez]

You can, but this requires a wideband lambda sensor. You could just try multiplying injection time by 2, it will be safe. They may have similar latency, but if it bogs down on idle try changing the latency to a lower value.

I dont know how you do that on a powerFc though.

Thanks for the reply. Fortunately I do have a wideband sensor. I was told there is a 'injector scaling' on the powerfc which sounds like it would accomplish what you suggested.

[rellik27]

May I ask why you are downgrading? also you can try finding an s15 power fc stock settings to match it up. Im runnning a d jetro also on an s14sr with stock almost everything lol.

[Croustibat]

Thanks for the reply. Fortunately I do have a wideband sensor. I was told there is a 'injector scaling' on the powerfc which sounds like it would accomplish what you suggested.

It will be easy then. If you see you are going leaner than 15/15.5 on cruise, enrich a bit. You need to be in the 12 or lower when booting it. Idle ... it can be lean, like 15-16-17.

Your timing and fueling maps depend on engine load, running a smaller turbo will just prevent from using the "highest" part of the maps, so timing wont be a problem. You could pull 2° if you feel the need to be safer.

[hstylez]

May I ask why you are downgrading? also you can try finding an s15 power fc stock settings to match it up. Im runnning a d jetro also on an s14sr with stock almost everything lol.

I'm building a track car and the output of the GT2871R is more than I need right now.

It will be easy then. If you see you are going leaner than 15/15.5 on cruise, enrich a bit. You need to be in the 12 or lower when booting it. Idle ... it can be lean, like 15-16-17.

Your timing and fueling maps depend on engine load, running a smaller turbo will just prevent from using the "highest" part of the maps, so timing wont be a problem. You could pull 2° if you feel the need to be safer.

Excellent. Thanks for the info. So do I want to be under 15 while cruising? I suppose that's my main concern since it's 100miles basically all highway.

[Blues13]

You can adjust the injector duty percentage on the Power FC commander or using Datalogit. It's under the settings. Just monitor the AFR if you can as mentioned and you should be fine off boost.

[jspaeth]

You can adjust the injector duty percentage on the Power FC commander or using Datalogit. It's under the settings. Just monitor the AFR if you can as mentioned and you should be fine off boost.


You don't need Dataogit to do this, you can very easily do this from the commander under Settings\Injector

[Blues13]

You don't need Dataogit to do this, you can very easily do this from the commander under Settings\Injector

I know.. I said commander OR datalogit..

[Biggamehit]

you selling the injectors?

[jspaeth]

I know.. I said commander OR datalogit..


That is completely my fault, I apologize for not reading your response carefully enough!

[Croustibat]

I'm building a track car and the output of the GT2871R is more than I need right now.



Excellent. Thanks for the info. So do I want to be under 15 while cruising? I suppose that's my main concern since it's 100miles basically all highway.

Depends on temp ... i mapped my engine to be at 14.5 / 15 on cruise and idle, and it works fine. Too rich is not good either, it washes out the top of the cylinders, resulting in cylinder wear at that place but not under. If you even have an egt gauge it is even better. Or you can monitor oil temp/water temp... if it rises too much, go a bit richer. If you cruise at 15:1 it should not be a problem though. Just dont drive at 120mph :D

[jspaeth]

Depends on temp ... i mapped my engine to be at 14.5 / 15 on cruise and idle, and it works fine. Too rich is not good either, it washes out the top of the cylinders, resulting in cylinder wear at that place but not under. If you even have an egt gauge it is even better. Or you can monitor oil temp/water temp... if it rises too much, go a bit richer. If you cruise at 15:1 it should not be a problem though. Just dont drive at 120mph :D


I have my AFR's setup to be in the 15.5-16.0 range under vacuum (enough vacuum to cruise at 75-80 in 5th gear without accelerating) then tapering down to 13.5 or 14.0 at 0 boost.........works really well, I get awesome gas mileage and never any knock.

Don't have an EGT gauge but can't imagine that this is a problem at all

[Kingtal0n]

I have my AFR's setup to be in the 15.5-16.0 range under vacuum (enough vacuum to cruise at 75-80 in 5th gear without accelerating) then tapering down to 13.5 or 14.0 at 0 boost.........works really well, I get awesome gas mileage and never any knock.

Don't have an EGT gauge but can't imagine that this is a problem at all

The factory has the A/F drop to around 12.5:1 (3" Hg) before boost. Just sayin' :zzz:

[inopsey]

The factory has the A/F drop to around 12.5:1 (3" Hg) before boost. Just sayin' :zzz:

the factory ecu also runs 10.1 or richer on 13 psi and holds that afr from the second it makes boost. everyone knows factory ecus are very safe and designed to be reliable for 99% of the factory engines at the cost of peak power.

[Kingtal0n]

the factory ecu also runs 10.1 or richer on 13 psi and holds that afr from the second it makes boost. everyone knows factory ecus are very safe and designed to be reliable for 99% of the factory engines at the cost of peak power.

Yeah, whats wrong with that? How much power do we lose for that safety? I am not saying dump 10:1 at 13psi- but a little safety net during spool is not a bad thing.

[jspaeth]

Yeah, whats wrong with that? How much power do we lose for that safety? I am not saying dump 10:1 at 13psi- but a little safety net during spool is not a bad thing.

I agree with the safety net thing, but I don't thing 13.5 is an issue at 0 bosot. I've never once gotten ANY knock.....then again, maybe my timing at that level of manifold pressure is very conservative....?

[Kingtal0n]

I agree with the safety net thing, but I don't thing 13.5 is an issue at 0 bosot. I've never once gotten ANY knock.....then again, maybe my timing at that level of manifold pressure is very conservative....?

Oh no, I never said you were wrong or indicated any argument. You can get away with 14.2 usually even at 7psi even on a stock T-25 as long as you at least have some plumbing length, like with a side mount. SR20 engines are very tolerable of a wide range of operating conditions. But conditions change, it gets hot sometimes, going up hill, in fifth gear, and we hit those load conditions as "going into boost" which translates to "spool time" where the subtle lack of fuel rears it's head as a cylinder pressure spike eats away at your internals perhaps without registering any knock.

I was just pointing out a margin of safety- something that we like to keep as large as possible, right?- that is nearly free to own (nearly: you DO pay for the extra fuel). Not many margins of safety are free, for instance forged pistons are added to an engine to increase safety margin sometimes at the cost of performance). But they are far from "free".

[jspaeth]

Oh no, I never said you were wrong or indicated any argument. You can get away with 14.2 usually even at 7psi even on a stock T-25 as long as you at least have some plumbing length, like with a side mount. SR20 engines are very tolerable of a wide range of operating conditions. But conditions change, it gets hot sometimes, going up hill, in fifth gear, and we hit those load conditions as "going into boost" which translates to "spool time" where the subtle lack of fuel rears it's head as a cylinder pressure spike eats away at your internals perhaps without registering any knock.

I was just pointing out a margin of safety- something that we like to keep as large as possible, right?- that is nearly free to own (nearly: you DO pay for the extra fuel). Not many margins of safety are free, for instance forged pistons are added to an engine to increase safety margin sometimes at the cost of performance). But they are far from "free".

Yeah, that is all correct.

now, in a completely unrelated side story, my AFRs for boost >14 psi are literally in the low 10s.

now THAT has gotta be costing me something, right?

Still haven't gotten around to bringing them more into the 11.5 range

[hstylez]

Is the fact that I'm going from a tubular SS manifold to stock a cause for concern? If I was running a MAF I wouldn't be concerned at all however I'm running the Power FC with the MAP setup..