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Discussion Starter #1
I know 13:1 A/F is "not a means to an end, but rather a guide" My car likes to make more power on the leaner side. i also can't get rid of my midrange torque dip.

See below:
http://www.villagephotos.com/viewimage.asp?id_=557629&selected=49363

So much for having a nice flat torque curve. This session i reduced fuel pressure from 58psi vaccume off to 45 psi vaccume off and reset all my VAFC settings.

Max power:175.4Max Torque;125.2

compared to the last one:
http://www.villagephotos.com/viewimage.asp?id_=523387&selected=49363

Any input would be greatly appreciated
 

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looks like your car enjoys 14:1 AF ratio.

The kicker is how much the power dies after 7000 rpm. What's the injector size again? (sorry I get a ton of these questions with dynos in the email and PM on all 3 boards I mod on and it's just a blur to me which one.you've upgraded your header, fpr, vafc, 310 injectors, cam gears, cat,(2.5 in. exhaust..right?). BTW what were you expecting in terms of power and powerband location?
 

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The actual curves don't look all that much different. It's tough to gauge without overlaying them on the same scale. In the first photo remember the torque curve is greatly exaggerated by the smaller scale and it looks more wild than it really is.
 

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Discussion Starter #5
i just want a nice flat torque curve without running dangerously lean.

My tuned set up:
99GSR -OBD2-
ITR AEM CAI
Skuk2 IM
RC 310cc injectors
Walbro 255lph Fuel pump
AEM FPR set at 58psi
Skunk2 stage 1 cams
Skunk2 cam gears Intake +2, Exaust-1
VAFC "All Ne points leaned; some quite a bit"
JDM ITR header
Mugen exaust
 

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I can only advise people to lean to what they are comfortable with. I agree that most people would hold off at 13.5:1-13.8:1 max. and leave a margin of error. Have you done a compression test recently?

If you have an emulator or datalogger to read the ECU fuel table and a wideband, that helps a great deal, since you can see how much the injectors are staying open or being pushed as the rpms go up. The duty cycle readouts as the rpms climb can tell you a great deal. So does engine temp and IM vacuum.

What is concerning to me is the sudden drop in power after 6800 rpm suggesting that the injectors are not spraying properly then or that you have not leaned out enough. I think you have to pinpoint which of these 2 are playing a factor. Greg Sumaroo told me that the reason you get big injectors when you don't have the luxury of an ECU reprogram is so you CAN fine tune the duty cycle to the lower level needed and lean down a lot. Leaning down is much more precise a control than trying to push an injector that is too small to flow more.

Many people I know with much more CR than you run leaner than that and 13.8-14.0:1 is around their limit. Looking at your AF ratio and where your torque IS flat says that your engine likes 14.0:1. You are at around 13.4-13.5:1 in these areas where you made less torque.

It's really YOUR decision as to whether you are comfortable with going further. I can't advise you on that, nor can I hold any liability for that. 175 whp is not bad for your setup but I suspect the engine has 185-188 whp in her with that package. But to find 10-13 more whp is asking for something you don't have in your pocket tuning wise.

Notice that when you dropped the FP by quite a bit, the power curve did not substantially change, suggesting to me you are giving a lot of fuel, especially with the big pump and big injectors.

If you try 13.8:1 and see a torque improvement in the area around VTEC switch and after 6800 rpm, that should tell you something. Do it in gentle incremements and stop when you hit 14.0:1 as a max. or when you think she's pushing her luck. I'd keep an attentive eye on your engine temps as you get leaner and leaner. If you see a sudden jump in temp, then I would back off immediately and not push the leaning process.
I agree with you that leaning in the upper rpms would make me nervous too. Monitor and listen to what your engine tells you.

Why haven't you pushed your cam overlap? +2 IN, -1 EX is nothing with the stage 1 Skunk2's. Have you tried +4-6, or even +8 IN? Have you tried -4 EX?

not much more I can add to that...

good luck...
 

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Discussion Starter #7
With a 14:1 AF, what should i set the ignition timing at given how lean it is? Would 18 degrees still be OK?
 

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well your ignition map will roll back some timing if you are pushing it. Put it this way, you ran 18 degrees BTDC with 14:1 AF and had no problems. If you are concerned then, you can roll it back to 17 but I don't think that is necessary.

The knock sensor works up to 4000 rpm and won't pick up any detonation above that rpm level since it can't tell the difference from normal engine noise at higher rpm.

Go in small steps, keep an eye on the temp, and target those rpm ranges on your VAFC where it is dipping. i.e. around VTEC and after 6800 rpm.

I would try + 4-6 on the intake cam and play with the exhaust cam. try more - retard to -4 to -5.. going + on the exhaust side adds more up top. +5 and +5 on both cams is not an unusual setup BTW...But I would see what +5 IN and -4 EX gets you versus +5 IN , +4 EX after you are done with the fuel. Don't forget to redo the ignition timing after you have moved the intake cam gear.
 

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Discussion Starter #9
I tried +4 -6 on the cam gears just for sh*ts and gigles and the car wouldn't idle right. Also when i set my intake cam to zero i dont't get ant more check engine lights. "Code 45 system too rich /too lean.
 

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Discussion Starter #11
As far as the CE lights...i'm getting them reguardless of cam gear settings. My motor has some hesitaion at idle. I tried messing with the TB screw, but it did not help. Also, my FP flucktuates 1-2 psi at idle. I might have gotten a defective Walbro 255lph fuel pump; or my RC 310's might not be spraying right. Or, my evap solenoid valve might be messed up because i'm purging inconsitantly.

I did not mess with the TB screw with the cam gears at +4,-6; i'll give it a try.
 

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I've never been a big fan of Walmart...I mean Walbro fuel pumps. NOS, Paxton, and Bosch are good alternatives. I run a Porsche 911 Bosch fuel pump.Weeeeeeeeee is all you hear at idle...damn fuel pump is a symphany to my ears...annoys the hell out of my non-hot rod passenger friends though..LOL.
 

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The concern is the nosedive your hp takes up top. Most common causes are too much exhaust gas getting trapped in the cylinder and not being removed or valve float.

To correct the former problem, a common tuning trick is to advance the exhaust cam to open it earlier when the piston is at BDC. We know that the low rod ratio engines don't really have a lot of piston speed at BDC as they start on the way up and so, opening the exhaust valve earlier may help remove the gases trapped. Your JDM 4-1/2.5 in. exhaust should not be holding you back.

Now the concerning part is the possibility of valve float as the other possible cause of the top end nose dive in hp. Did you replace you valvesprings or are you using stock GSR ones with the Skunk2 Stage 1 cams?

Stiffer Skunk2 springs with retainers will help if this is the cause.

I already suggested that you try a wide lobe separation angle, lean down the fuel pressure, and advance the exhaust cam. If that does not help then you may want to invest in some valvesprings if you have not done so.
 
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