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It's clear the 951 was adequately designed for street performance and some racing. At 2.5L, the stock intake and exhaust were sufficient to provide the advertised power. Large power gains, however, generally require increasing airflow capabilities, both in and out.
That said, many want increased performance and choose to use many of the stock components. Keeping the 951 intake manifold, throttle body, intercooler and piping, stock exhaust and running pump gas may be due to budget constraints or the desire to maintain a stock appearance. We knew them as ‘sleepers’ back in the day. So, given these restrictions, will the 944 2V turbo still make good power? Is it like breathing through a straw?
Here are dyno results from such an engine. The higher RPM power is limited by the restricted airflow, but it’s still
got plenty of grunt. It’s also a sound platform for future mods. I strongly suspect that allowing more air in and out of this basic engine will wake a sleeping giant.
Any idea what feet per second flow is at a 944T throttle body, intake runner or port...?
Other than a software that ciphers this using other inputs, is there a sensor that can measure this..?
The software from that guy Larry Meaux from Abbeville , La that I mentioned can tell you which component is the choke point.
I have a free single key for his original software and an offer from him for 3 authorization keys for 3 separate PCs for the newest version for a cheap price if you are interested in experimenting with it.
I fooled with some simulation software years ago and patterned some design parameters around the outputs. In the end, I decided that only the dyno knows for sure. That said, there is VERY sophisticated (and VERY expensive) simulation software available today that I'm sure is far superior to what I fooled with, but I have no experience with it.
I suspect the biggest restriction is the AFM, followed by the throttle body diameter along with the (small diameter) intercooler piping. The intake falls in there somewhere too.
But the point is, very respectable power can still be made using these less than ideal components.
I made 450/475rwhp/t on a dynojet using a stock intake, stock intercooler, stock intercooler pipes, stock throttle body, and probably closer to 20psi. I used a MAF however. I'd think the opening to the stock air filter box is the single biggest restriction. The AFM barn door seem much bigger by comparison, no?
right, but the inlet 50x60 at airbox after filter/entrance to AFM is still ahead of the barn door, so the air hitting the door is already "restricted", the door just makes it worse (until ~4500 rpm or so when it goes WFO too).
Tom, i'd bet if you did that same run again, then just swapped the airbox for a cone filter in the same location (even with the hot air intake) you'd pick up 2-3 psi, or just more HP at the same 20psi level depending on how the boost is regulated.
right, but the inlet 50x60 at airbox after filter/entrance to AFM is still ahead of the barn door, so the air hitting the door is already "restricted", the door just makes it worse (until ~4500 rpm or so when it goes WFO too).
Tom, i'd bet if you did that same run again, then just swapped the airbox for a cone filter in the same location (even with the hot air intake) you'd pick up 2-3 psi, or just more HP at the same 20psi level depending on how the boost is regulated.
Just to be clear, the 450/475 run was with a cone filter on a MAF. The airbox filter opening has less area than a 50x60 opening for sure (it's close in area to the stock i/c pipes), and the air isn't pressurized. How the shapes affect flow is above my pay grade though...
I ran a motor almost exactly like Michael describes in my race car for almost 15 years. It was a strong, reliable motor, and in a 2400# car, it goes pretty well.
Since the outlet is on the pressurized side, what difference would it make if the rest of the hosing between the turbo and intake manifold would be the same diameter? If you put bigger ID hose on workshop compressor, is there any benefit on the other side of the hose @ full flow? I doubt it. Compressor outlet valve is the bottle neck in flow and so is the turbo outlet diameter. IMO.
Or to make it actual; I'm going to plumb turbo directly in intake manifold the only part between the two will be TB. Since stock TB is bigger ID than turbo outlet, how or why would I benefit from even bigger ID TB?
My 3.0L did 418hp and 444 ft/lb torque on Dyno Jet at well over 4000ft elevation using the Mafterburner. Ran 15lbs boost.
94 Octane fuel
I switched to Mtune but engine is out of the car right now
Since the outlet is on the pressurized side, what difference would it make if the rest of the hosing between the turbo and intake manifold would be the same diameter? If you put bigger ID hose on workshop compressor, is there any benefit on the other side of the hose @ full flow? I doubt it. Compressor outlet valve is the bottle neck in flow and so is the turbo outlet diameter. IMO.
Or to make it actual; I'm going to plumb turbo directly in intake manifold the only part between the two will be TB. Since stock TB is bigger ID than turbo outlet, how or why would I benefit from even bigger ID TB?
air compressor only puts out what, 5 cfm at 120psi for a big one? the pump isn't made for higher flow, a turbo is.
turbo straight into manifold...bigger TB would be beneficial for the 90% of the time the car is driven "N/A"
Since the outlet is on the pressurized side, what difference would it make if the rest of the hosing between the turbo and intake manifold would be the same diameter? If you put bigger ID hose on workshop compressor, is there any benefit on the other side of the hose @ full flow? I doubt it. Compressor outlet valve is the bottle neck in flow and so is the turbo outlet diameter. IMO.
Or to make it actual; I'm going to plumb turbo directly in intake manifold the only part between the two will be TB. Since stock TB is bigger ID than turbo outlet, how or why would I benefit from even bigger ID TB?
Because the length of the pipe/hose matters when looking at total pressure drop. The throttle body and turbo outlet have a very short length, so their diameter and restriction add up to a small amount of total pressure loss. OTOH, if the intercooler pipes, intake, and especially the exhaust are too small, the total pressure drop will add up quickly.
BTW the sonic choke point is raised slightly when flowing dense, pressurized air in a turbo engine. That's why you can simply raise the boost and make more power on a stock head.
07-01-2018, 06:46 PM
3L turbo with stock AFM and 951 intake?
