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YOUR RESEARCHMy C4s dyno chart
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Install on he car now so i'll leave this intake
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Performed · outcome unconfirmed · Original poster
I'm having cats installed on he car now so I'll leave this intake on and do a after dyno run to see the difference with the cats.
Leading evidence: 'Install on he car now so i'll leave this intake' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Install on he car now so i'll leave this intake' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
Jake I just had the plugs changed about 2k miles ago.
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Performed · outcome unconfirmed · Original poster
I'm using the bracket that evoms sells currently, so it's kind of out of the way.
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So I put the car on the dyno to see how she was doing power wise. She made 299.3 wheel horse power and 254 torque. Relatively good power although it sucks it didn't break 300 by .7 horsepower. My only concern is the 5th gear shift. It seems scattered. The tech suggested maybe my clutch was slipping. The clutch/rms were replaced at 80k. Ims bearing done at 121k I'm now at 129k. Seems a bit premature. I'm not a professional manual TRANSMISSON driver but I don't know what I'm looking for for signs of slippage. I had the oil analyzed to make sure it wasn't anything bad, and black stone said my oil is near perfect. Any ideas guys?
My 2nd hand info is the dyno run doesn't involve shifting at least under power.
The dyno rollers are started spinning with gentle acceleration maybe starting out in 1st gear and going up through the gears shifting at lower RPMs than one would shift at on the road until the tranny is in the gear desired for the dyno pull. This wants to be the gear that is as close to 1:1 without being under. One wants to avoid any torque multiplication by a lower gear ratio than 1:1.
However, IIRC the 996 gearbox doesn't have a 1:1 gear. 4th is under 1:1 and 5th is a bit over 1:1. So 5th gear I believe should be the gear you use for the dyno pull.
What probably happened is when you shifted the rear tires spun a bit on the dyno rollers.
The way the plots flat lined, either the engine is out of air, the ignition is seeing safety retardation, you have a bad knock sensor, or the clutch is slipping.
Those plots are too jiggly for me, looks like the ignition is scattered. I'd change the spark plugs.
Jake I just had the plugs changed about 2k miles ago. I have been getting a misfire in cylinder 1 and 6 lately. Maybe coils? I was hoping for a more linear graph than this.
Very interesting results. I think I have the same intake in my car so I'll be very curious to see what the findings are here. This is not just a smoothness issue - your engine/powerband hit a wall around 6400rpm that shouldn't be there.
Try it and see. The 3.8S trumps them all in my experience. My wife set all 5 of her speed records with the 3.8S, the car picked up 3 MPH once I got rid of the same unit that you have now. Dataloging MAF voltages was the only way I figured it out.
3.8 s intake ordered. I'm having cats installed on he car now so I'll leave this intake on and do a after dyno run to see the difference with the cats. THEN I'll install the 3.8s intake and see how that plays out afterwards. I'll keep everyone informed about this as it progresses. Thanks Jake for the knowledge/advice.
if it doesn't work then you're the first person i will contact Jake. I really do hope that the air box fixes the turbulence with the power delivery of the car. I wasn't paying attention to the flat spot at 6500 rpm, i was more concerned with the jaggedness of the rpm in the 5800 rpm area. The guy who did the dyno run was questioning the integrity of the clutch "slipping" in 5th gear. I haven't noticed any slippage while driving though.
Hey Jake. Quick question. Im trying to install the 3.8 air box and I'm having figment issues. The hood will not close. Could it be that my gt3 throttle body/iPd throttle body hose is causing it or am I just being stupid and it's not seated right somewhere? The front bolt attachment lines up with the air box.
Few things I've found when re installing the airbox:
- make sure it's not sitting on any cables or pipes
- make sure that the two locating pins are correctly seated in the rubber grommets
Other than that I'm not too sure, hope that helps!
The 996 decklid has an intake gasket accordion thingy. The 997 decklid has an intake gasket smooth thingy. Could this be your clearance problem?
996 intake seal
997 intake seal
Could the squiggles be caused by the viscous front diff?
Since its a mechanical operation, I wonder if it 'kicking in' happens on the dyno as the fluid warms up underload.
Were the rollers locked so they run at the same speed?
Dyno was calibrated a few days before hand. My other reasoning for this is because I'm trying to figure out why I have flat spot in the upper rpm area. Trying to rule out the cheaper potential fixes now.
Ok so I refit the air box in the car. Tried it in stages. Bottom for oerfectly. Top without the theottle body hosing fits ok. It gets snagged on the snorkel when I open the deck lid. Swapped the old snorkel to see if that's it. Still the same. So I have it in the car now. My theottle body hose that's supplied by ipd is too big. The the bigger theottle body I can't reuse the stock hose. So it's the throttle body hosing that pushes the air box to the rear of the car. Fml
That's interesting to note. I have a bored out stock TB using the regular IPD plenum and didn't have any issues IIRC when I had my 3.8 intake on awhile ago.
Utilizing the stock theottle body only changes the inside diameter. I have the gt3 theottle body on the car which seems to be the limiting factor in the swap. I haven't seen any people with the 997 air box with a bigger throttle body. This sucks.
