Thebestmotoring

I got my PFC tuned by SR for stock twins, ic and full exhaust, etc. The basic bolt on. My question is do I need to retune my PFC if I switch to the Pettit High flow turbos? Anyone had this mod done?

T.I.A.

Ken

cewrx7r1

iTrader: (2)

From Pettit:

"Hybrid stock turbo unit provides an 8-10% improved flow rate. Hybrid hi flow turbo unit provides a 15-20% improved flow rate."

What these will do are:
(1) allow the engine to build boost faster
(2) increase the max boost that can be made
(3) for a given boost, should run at a slightly cooler temp

I see no reason to change anything if the rest of your engine setup is not changed. Factors 1 & 2 do not affect the engine's breathing capacity.
#3 might slightly increase the charge density but nothing like compared to runnning a single turbo.

Thebestmotoring

Hi Chuck,

Thanks for the info. Would the increase of flow rate 15-20% equal to amount of HP the engine will increase?
Is the inj. lag time to .04 good for the upgraded the 1300cc sec. inj. ?

Best regards,

Ken

cewrx7r1

iTrader: (2)

The improved posible flow rate does not increase power. It only builds boost faster and allows you to run higher boost more safely befor overtaxing the turbos. A porting change or boost change affects power. Just because it has the potential does not mean it will do it. If you run the same boost after as prior to the turbo upgrade the only affect will be that slightly cooler charge.

JoeD

yes, you do need to remap your PFC. the upgraded turbos flow more, which means more air is being sucked into your engine, and the exhaust is more free-flowing. these turbos are not just for cooler running and higher boost. its kinda like adding a single turbo.

cewrx7r1

iTrader: (2)

The engine will not "BREATH" more if the same boost is run after the upgrade as before. At the same boost level, only the intake charge temp will be diff with the new turbos as compared to before and that will not be that much different unless the older turbos were being run at their maximum.

Tim Benton

iTrader: (1)

This thread seems to be going of the way of "a single pushing 14 psi, and the stock twins pushing 14 psi, why does the single make 400 hp, while the stock twins only make 350 or 360 rwhp." they are both making 14 psi, but is the cooler charge air making that extra 40 HP? I don't think so.

Tim Benton

racedriver

cewrx7r1

you are wrong dude

higher flow is due to bigger compressor wheel, hence more air into motor, hence more fuel required.

but since its not a big upgrade, and most of the maps are overly rich, it might work. i'd lower the boost, take it to a dyno, then slowly raise it while keeping an eye on air fuel readings.

cewrx7r1

iTrader: (2)

Let's say I have an engine and the PFC is tuned well and all runs well.
If I adjust the boost to 10, 12, 14, or 16PSI, the engine will run well at each boost level producing more HP as the boost goes up. Remember our PFC can handle boost up to 19.4PSI at row 20 if correctly programmed.

Now I replace only the turbos (which have been upgraded to flow more) and the WG had been preset before the change to produce 10PSI boost.

What happens when I run the new turbos? Since they are more efficient and flow more, my engine will no longer be running 10PSI, it might jump up to 12PSI. Since my PFC is already programmed to run 12PSI, what is the difference? The only difference will be in the temperature of the intake charge. That will not be that much unless my IC was too small to begin with. Now since I normally run 10PSI, I reset the boost down to 10 again.

Now do I really have to make any changes to the PFC? .

racedriver

wrong again dude

after you change turbos you will still be at 10 psi, because that is controlled by the wastegate, whether the turbo is big or small doesn't matter and won't raise the boost. The turbo is modified to push more air into the engine than before, all things being equal.So at the same boost(pressure inside the plenum) level a greater VOLUME of air is going into the motor. What you may be thinking is this:
The hybrid big turbos will produce the same power as stock ones at a LOWER boost level, say 8 lbs vs 10 lbs.That would cause a cooler charge and no extra fuel would be needed.

adax

iTrader: (2)

All things being equal as you say, (boost pressure and intake/exhaust tract resistance) there is no way you can get more "volume" in there with higher "flowing" turbos. It's a law of physics: Q=P/R, also equivalent to Ohm's law: I=V/R which cannot be broken. Key is that the resistance typically decreases a lot on the exhaust side, increasing volumetric efficiency, when going to a single turbo so you do achieve more flow. I believe this is the main reason why you feel the big power increase when both turbos are online in sequential mode.

Alan

Chadwick

iTrader: (12)

Hmm…Ok, I got an upgraded air compressor for Christmas. When running it can produce 150psi. My old one was rated at 90psi. I had them both hooked up to a 25 gallon tank and set the pressure gage at 50psi. I then emptied the tank of air, hooked them up to a tire and let them rip. My new compressor filled up the tire in 23 seconds. My old one took 27. When I measure the air in the tire it was 50lbs. Now why in the hell would it be 50lbs for both compressors, my new compressor flows almost 50% more air!!!

Dan

cewrx7r1

iTrader: (2)

It is evident that RACEDRIVER? does not know what he speaks of. First he said one thing now he says another.

As I have previously stated: The only increase of volume would be caused by the cooler intake charge.

Let's us just ignore him from now on!

Mach2

Adax,
what does I=V/R have to do with this? In case you didn't know, that formula gives you the current in a circuit while knowing the electrical potential and the resistance. I think you got confused there. If you didn't know this, you could have noticed it when you typed "Ohm's Law", which is the unit used to measure resistance, which applies to circuits, and not thermodynamics.

racedriver

I refuse to have this argument until someone shows me their degree in mechanical engineering. Then i will accept their apology. Goood day and Merry Christmas to all.

adax

iTrader: (2)

I mention Ohm's law because it's conceptually the same. The flow (electron current or air) is equal to the potential difference (voltage or pressure) divided by the resistance (electrical or mechanical). You can ONLY increase flow by increasing pressure or decreasing resistance.

I don't have an electronic copy of my degree, sorry. It's in biomedical engineering anyway, but this is pretty elementary stuff.

Alan

mmaragos

Doesn't it depend on what the limiting factor was before the change? If the stock turbos were the flow-limiting factor and the new turbos were able to flow more, then wouldn't the net result mean more airflow through the system? Or if the engine, exhaust, or intake was the limiting factor, then better flowing turbos would allow higher boost, faster boost and/or cooler boost...but not more flow?

newRX7fan

iTrader: (1)

Adax-

I think you and racedriver are saying the same thing, just using different (and maybe not technically correct) terminology. The idea is more flow at the same boost because of less resistance. And as a previous post pointed out, if the stock turbine was limiting flow (ie preventing VE from being larger), putting a better flowing one on would decrease the resistance.

JoeD

cewrx7r1, im affraid you are wrong.

the Pettit Turbos are higher flowing than stock, meaning that they flow more air at any given psi than stock turbos. if you dyno an FD and get 340 RWHP for example, then dyno the same exact car with the only change being upgraded turbos, and dyno it at the same exact level of boost...the one with the Pettit Turbos it will make MORE power than 340 RWHP.

think of upgraded turbos as a single. same thing. they both flow more CFM at any given psi than stock turbos. why do you think FDs with upgraded twins usually make more power than an FD with stock twins.

so Ken, the correct answer is yes...if you dont worry about popping your otor, i suggest you get the PFC tuned for your upgraded twins.

cewrx7r1

iTrader: (2)

The original question had to do with Ken's current setup which is very conservative. Thus the affect is nill.

Now you are jumping to the extremes assuming that his old turbos were running at their max capacity into a gigantic breathing engine. Even so you are getting your facts messed up. With a fixed system of resistance, flow volume will remain equal for the same pressure and temperature of the flow medium. It does not matter what size turbo creates this set pressure at this set temperature.

What the larger turbo has to offer is more total flow capacity at lower temperatures. On an engine that has conservative breathing, the increased capacity of the larger turbo is really not utilized. As you increase the breathing capacity of the engine, a point is reached where the smaller turbo becomes less efficient and can not suppply the volume and that which it does is overheated.

All my remarks have been to Ken's application, not to joed and racedrivers imagination.