partial throttle driving with hondata/larger injectors.

Hondata installation questions / answers / issues.
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Joined: Thu Aug 29, 2002 3:04 pm

partial throttle driving with hondata/larger injectors.

Post by rev012 »

Happens more in higher gears at partial throttle. Lets say I'm cruising in 4th, as I go from 3500-4500 RMP and hold the gas pedal steady (partial throttle, applied slightly) the car jerks as if I hit the pedal in all of the sudden, but I don't, it just simulates that for that .1 of second. Anyone knows what causes that/how to fix it/problems from not fixing it?

N/A b18c5 with p72,hondata.

Before the problem: stock 240cc injectors, stock f.p.r. and 16 ignition base timing
Problem started after the following installed/changed: 370cc injectors, b&m f.p.r set 5-6 psi lower,18ignition base timing
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Post by ronin »

mine does that now, my box was tuned to run my jrsc, and now i'm back to n/a, with cams pistons, etc, etc...
440cc, no fpr, fuel and timing not "ideal"
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Post by blownintegra »

Yeah, my car does EXACTLY the same thing. On the highway it gets only average mileage, not the 30 mpg everyone claims. It feels like surging. If you watch the A/F gauge, it surges as the car goes rich to lean, rich to lean. Only when it goes into boost and the A/F goes into green (rich), even light boost, does the car finally not surge. It does seem to go into rich boosting stage, very rich and very early. This was supposed to have been tuned with the new duration figures for the 440cc injectors. I was hoping for some closer to stock drivability out of boost, and better mileage than I am getting now. My car is an LS with a JRSC, and it almost seemed to run better stock with the adjustable FPR, but now the transition into boost is smoother with the Hondata. I wish I could get the Fuel map and Ignition map for my car and have someone analyze it to tell me where I might obviously be needing some more adjustment. It was tuned on a dyno, so the HP on the top is there, but the 80-95% of driving is done part throttle, and my car seems a little flat, burns too much gas in normal driving, and sure surges like a biatch.

So dude, your not the only one.....

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Post by Hondata »

Tuning part throttle usually takes me 2-4 times longer than full throttle tuning. If you just tuned for full throttle on the dyno, then you're only half way there.

First check that your TPS is adjusted correctly, as this can give cut in/out problems, but usually only on very light throttle.

The problem is closed loop operation. If you have one area of the fuel tables which run either rich or lean, then eventually the long term fuel adjustment will go the other way to compensate. e.g. if you're running rich at cruise, then the long term adjustment will take fuel out. This is fine as long as the whole fuel table is the same mixture. If the fuel table is 'bumpy' mixture wise, then when you change rpm or load to another area, the mixture can go quite rich or lean under closed loop operation and you'll get some sort of hesitation. The worst case is where you have a rich and lean spot close to each other. Say you run in the rich spot so the long term adjustment takes out 20% fuel, then change speed so you're in the lean spot. The lean spot is now 20% leaner again thanks to the long term adjustment, and you'll experience hesitation.

The solution is to tune part throttle with close loop switched off using a wide band lambda meter. You must tune to 14.7:1 where ever the ECU will run closed loop, as it will adjust the mixture to 14.7:1 there anyhow. Once you are done, switch back into closed loop, and datalog the short and long term mixture adjustments to see how well you have done. Short term adjustment should be -10 to +10%, and long term should be from -7% to +7% BTW you don't have to run closed loop - sometimes you want to run richer mixtures than 14.7:1 at part throttle to keep the turbo temperature down.