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Increase Rev Limit on Stock ECU

Old 03-19-04, 02:37 PM
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Increase Rev Limit on Stock ECU

In the back of Grassroots Motorsports there is an ad that talks about a $100 fix that increases the rev limit on a stock ECU. Don't know about this, so thought I would ask hear.

Does anyone know how to increase or remove the rev limiter on a N/A 1988 ecu. Don't want to change the mapping just increase the rev limit to 8100rpm. If I can get to 8100 rpm it saves 4 shifts a lap and helps the rpm drop into the next higher gear. All of the ITS runners seem to rev higher than the stock rev limit of 7800 rpm so they must know something I don't know. Thanks in advance.
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Old 03-19-04, 03:25 PM
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im new to this site!
and was wundering if anybody knows were i can find info on auto-X in bc canada! i was just wondering because i love racing and haulin *** on back roads around here(fort st. john B.C.) and figured my skillz would be better off in legal racing LOL.
so any info (on sites or places to phone) would be greatly appreciated! (and i was wundering if my car would be able to race any classes (its an 89 isuzu I-mark RS with the lotus handling package)its a fun front wheel drive
thanx and sorry for blabbing on
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Old 03-20-04, 04:15 PM
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hey, imark, if you want to ask a question, make your own post, its up at the topright part of the page...

anyways, i wasnt aware that there even was a rev limiter on 2nd gens...if I rev it all the way, mine goes past where the 8k tach will read, and since i removed (by force) my buzzer, it doesnt complain at me when i do it...and now that my engine is getting bridgeported, i think i will need a different tach, because my shop says it will rev alot higher than stock, with the na ecu.
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Old 03-21-04, 06:14 AM
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I once heard someone say that the FC has a "soft" rev limiter. I guess that it means it doesn't bounce off it like some other cars I have heard. The ad in Grassroots is from a reputable individual. I plan on sending my ECU to him in the next couple of weeks. I seem to be cutting out at the top end so I want to see if this will help.
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Old 03-21-04, 07:48 AM
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Soft Limiter

I believe that all FC's have a soft limiter at 7800 RPM. I can push mine through it for a couple of hundred rpm using the acceleration momentum of the car but it just bounces off it at slower vehicle speeds.

Just want to know how to overcome it. I am putting on a fuel control system (Megasquirt) and now need to know how to get that last 400 rpm out of the ignition system.

Anyone who can help, I thank you in advance.
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Old 03-21-04, 06:13 PM
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auto-X tracks in northern BC or AB canada

Im new both here and to the import car scene!(i hate civics) And was wanting to get some info on any northern British Columbia, or Alberta (canada) tracks! We have a nice drag strip here but i whant corners!LOL ! Theres some pretty awsome back roads out here!

And if any one knows were i can find some aftermarket companies who make(still make) mods(coil overs/intake/clutch/cams etc.) for any isuzu cars(an 89 I-mark RS) i cant find anything. Im practicing with fiberglass, and making a spoiler(not huge) and then a wide body kit, and fenders and my hood! (i seen it on tv, they made cobra hood and fenders) So ity would be awsome if any of you guys could please help!
thanx! (maybe) LOL j/k
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Old 03-21-04, 09:24 PM
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hmm, weird i didnt know about the soft limiter, you learn somthing new every day! time to think of which route i want to go to get rid of it....

oh, and imark, seriously, if you want to be all eccentric on someones thread, at least make it relavant to the subject that was originally posted...
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Old 03-22-04, 09:37 AM
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Thanks for the Information, IMark

I am going to give you the benefit of the doubt seeing as you can respond to my thread, that you understand how this site works and the type of car we are talking about. If you want to discuss Isuzu IMarks find a site that covers that car or go on a website that discusses B.C. Slaloming. Try a site associated with the CACC (local) snctioning body.

Anyways, someone must have some information for me. My first on track day is April 17th. Thanks.
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Old 03-22-04, 11:37 AM
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onenof the only ways i would figure you could gain the extra 400rpm out of ignition would bo to either re-program the ecu...check with MSD...to see what kind of ignition advance/duration aftermarket ignition/coil systems they may offer..or what about running some type of engine management system (this is where you can set everything from timing to air/feul etc.) another thing you could look at is:is there anything mechanically restricting any flow ( exaust,throttlebody,injector size,etc.) even if you are able to bypass rev limiting;is there enough power/torgue to jusitfy whaty you are asking....who about your bottom end (bearings??) for every give thee has to be a take (if you know what i mean) i'll be honest this is the first rotory i've owned and i have always been under the hood of a piston type intern. cumbust.;but if you can understand the basic therory and principals of the wankle engine,you can still emply many of the same therories and prospectives as the other......i find you just take a different approach.
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Old 03-22-04, 02:14 PM
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Thanks.

I appreciate your efforts. The car is very well prepared and all of those maintenance issues/ modification efforts have been taken care of. I will have programable fuel injection but not ignition.

I am not looking for the moon, just a little more RPM. I have worked it out in my track simulation program that 300 rpm higher rev limit will save me 6 shifts a lap, or 3 periods at rev limiter. This allows me to pick up over .5 second at Mosport and potentially 1 second at Shannonville.

This is why I am looking at this opportunity 300 rpm is worth more to me in time savings than 20 hp.
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Old 03-22-04, 05:30 PM
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Maybe try contacting grassrootsmotorsports about their little 100 dollar trick.

Or else another way would be to acquire an ECU and TPS from a 1989 or later NA rx7 and swaping it for your 88 NA ECU.
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Old 03-23-04, 11:20 AM
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Won't work, you need all kinds of crap if you swap ECUs..

If you find out how, please post it here.. I need to do this to mine as well..

PaulC
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Old 04-02-04, 01:00 AM
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Indeed...I'd like to know how to do this also.
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