View Poll Results: RPM raise between shifts?
YES --- Modified ECM (includes all after market EMS and piggyback and flash ECU)
93
30.49%
YES --- Modified clutch (all aftermarket clutch)
71
23.28%
YES --- Modifed MAF (convert to speed density)
18
5.90%
YES --- Modifed BOV (all after market BOV now or tried before)
91
29.84%
Yes --- All stock on above parts
95
31.15%
Not at all (includes stock or modified)
76
24.92%
Multiple Choice Poll. Voters: 305. You may not vote on this poll
RPM raise between shifts
That was my idea, I just couldn't explain it as well. 
Originally Posted by MalibuJack
...Anyway, what was happening is when the throttle blades snapped closed, it would momentarily go rich, then as the airflow restricted, it would go lean, and the engine speed would rise..
your right, this wouldn't happen all the time, what I did notice was when my car was cold and the induction system components haven't absorbed heat into them, they seemed to cause the metal bodied BOV on my car to "Stick slightly" or open slower than normal.. Once my car was up to operating temp, it didn't seem to hapen anymore (or at least I had trouble reproducing it)
The best thing I can gather from it is altering your airflow patterns and restrictions in your car, In the case of the BOV, its likely not venting completely and there's still some positive pressure in the upper intercooler pipe "forcing" its way through the idle circuit between shifts causing it to raise.. since there's no load in the engine between shifts, the engine speed rises as the air sneaks past...
your right, this wouldn't happen all the time, what I did notice was when my car was cold and the induction system components haven't absorbed heat into them, they seemed to cause the metal bodied BOV on my car to "Stick slightly" or open slower than normal.. Once my car was up to operating temp, it didn't seem to hapen anymore (or at least I had trouble reproducing it)
The best thing I can gather from it is altering your airflow patterns and restrictions in your car, In the case of the BOV, its likely not venting completely and there's still some positive pressure in the upper intercooler pipe "forcing" its way through the idle circuit between shifts causing it to raise.. since there's no load in the engine between shifts, the engine speed rises as the air sneaks past...
Originally Posted by 90GSX-03EVO
.....When you get off the gas for a split second before a gear change, while you are still in gear, the car actually goes into a form of fuel cut. It injects no fuel at all, and runs solely on transmission revolutions to keep the engine turning. As soon as the transmission is disconnected from the engine and it is no longer self sustained, the ECU "loads" the idle fuel map, which was made during warm weather. Cold air is more dense than hot air, so for that split second that combustion starts up again (before the MAS has time to meter and the ECU has time to do any corrections) you are effectively dumping in a bit too much fuel, and a bit too much air, which is the same as applying throttle..
Originally Posted by titaniumkingpin
sure buddy, weren't you the one who kept saying that it was driver error?
I said quite a few things. There were lots of possibilities that I threw out there. The only one that seemed to actually "stick" was the driver error.
If you go back and read ALL of my posts, instead of just the ones that offend you...
well if this is the BOV and wastegate issue, why is it still happening on the stock evo's with stock bov and wastegate.
I think it's got everything to do with the filter and maf sensing more dense and cold air when the weather gets colder.
I agree with most of it said about the momentary fuel cut etc.
I think it's also to do with the clutch since clutch has to do with this momentary fuel cut and if they're worn, they could create this situation and make it worst (more rpm rise) since their disengagement point isn't what it used to be.
but I'm in the process of trying another filter. Because even the weather is colder and the cars not warmed up, the problem goes away when you run the car without the filter on your stock airbox.
I think it's got everything to do with the filter and maf sensing more dense and cold air when the weather gets colder.
I agree with most of it said about the momentary fuel cut etc.
I think it's also to do with the clutch since clutch has to do with this momentary fuel cut and if they're worn, they could create this situation and make it worst (more rpm rise) since their disengagement point isn't what it used to be.
but I'm in the process of trying another filter. Because even the weather is colder and the cars not warmed up, the problem goes away when you run the car without the filter on your stock airbox.
Originally Posted by AdamsssEvo
Do not T into the bov line if you are using an after market boost controller.
If you did, try the other route and see if your rpm raises then.
If you did, try the other route and see if your rpm raises then.
Both of my Evo's have had boost controlers and boost gauges BOTH T'ed from the line between the intake manifold and the compressor bypass valve. No problems at all.
i'm having no problems but a little fluctuation in the boost. It'll taper to 21 psi before coming down to 20psi/20.5psi.
Sometimes it'll go up to 22psi or will just stay at 15 psi on first gear.
I heard putting it onto compressor nipple is another way to do it. few shop owners thinks so.
it's this long argument.
Sometimes it'll go up to 22psi or will just stay at 15 psi on first gear.
I heard putting it onto compressor nipple is another way to do it. few shop owners thinks so.
it's this long argument.
Just starting seeing the rpm raise a few days ago..its been cold and hasnt happened just started all of a sudden..what i am seeing mostly is rpm raise when i come to a stop,if i press the brake pedal it goes away..that is a weird one..but its getting worse now its doing it whenever i decelerate typically in lower gears 3-2 2-1 shift..the rpm raise if random anywhere from 2k rpm and sometimes all the way to 5k rpm..
Well.. for the people who were wondering why it would happen on a stock evo.. My theory with the wastegate/stock BOV is that the BOV and engine vacuum have an effect on it, but also the preload on the wastegate from the actuator.. too much preload could keep the wastegate flapper closed longer, and could allow boost to continue to build for a short time after throttle lift.. Therefore it will continue to draw a bit of air through the mAF sensor for a short period of time after throttle lift.. If your shifting at that moment (clutch-in) RPM's could rise as load is removed from the engine...
This is the ONLY reasonable theory I could think of that would apply to every car regardless of its modified or stock.
This is the ONLY reasonable theory I could think of that would apply to every car regardless of its modified or stock.
There can be some driver error involved though.. Some people don't completely lift when they shift, and as the clutch gets more wear, the RPM's can rise.. in my case thats certainly possible with the amount of mileage on my car. HOWEVER this only started happening when I changed BOV and went to a blowthrough sensor, which amplified a latency in airflow that would trigger the same anomoly that you folks are experiencing...
In my case, once all the hardware "warmed up" the symptom would go away completely, but also if I adjusted my timing of how I clutched and released the gas it also helped..
In my case, once all the hardware "warmed up" the symptom would go away completely, but also if I adjusted my timing of how I clutched and released the gas it also helped..
Originally Posted by craigbb
Just starting seeing the rpm raise a few days ago..its been cold and hasnt happened just started all of a sudden..what i am seeing mostly is rpm raise when i come to a stop,if i press the brake pedal it goes away..that is a weird one..but its getting worse now its doing it whenever i decelerate typically in lower gears 3-2 2-1 shift..the rpm raise if random anywhere from 2k rpm and sometimes all the way to 5k rpm..
Thats unusual, you should verify you clutch switch is still connected since the ECU is aware of the clutch switch and its "action" Also check your DV(BOV) and other vacuum connections, you could be experiencing a MAF anomoly or a leak in your case.
I think at least some percentage of this is due to the throttle peddle getting temporarily stuck under the floor mat. So, do this simple little thing and see if it goes away.... Take your drivers side floor mat out!
LOL thats true..
I was able to verify without a doubt on my car with the blowthrough sensor it was the BOV.. It has gone away since I swapped back my 1G BOV..
The excess pressure that wasnt venting was forcing its way into the engine even with the throttle blades closed (in some cases it was preventing the throttle from closing fast enough) and causing the RPM's to raise.
I was able to verify without a doubt on my car with the blowthrough sensor it was the BOV.. It has gone away since I swapped back my 1G BOV..
The excess pressure that wasnt venting was forcing its way into the engine even with the throttle blades closed (in some cases it was preventing the throttle from closing fast enough) and causing the RPM's to raise.
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Joined: Dec 2004
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I just purchased an MR as well and I think people are confusing this with the way the car is designed...The RPM's stay up after the clutch is engaged so you can better rev match...I believe people are slightly exxagerating this and it is actually something Mitsubishi designed for better ultimate performance...If you notice if you continue coasting in gear the revs will stay up for a little bit then the revs will suddenly surge to help slow the car down...I am not sure but it seems that the Electronic Brake Distribution comes on (Could be wrong but that is what it feels like)