Premature speed limit on KA24de. Need input.

[simmode1]

My KA seems to be randomly hitting it's speed/rpm limiter prematurely at random and/or intermitten intervals. It never happens at less than 85mph, but sometimes I can pass 85mph and it will kick in a little later.

I was wondering if this may be caused by my undersized wheel/tire diameter? I have 16x8.5+27's with 225/45/16's mounted on them. To keep the stock rolling diameter, I should have 50 profile tires on.

Could this be throwing off my speedo/ecu/whatever and making the governor kick in early? Opinions, plz.

[S13Joe]

Try disconnecting your speed sensor and see if that helps, if not check your grounds.

[Uberck]

you can try overnighting a jdm ungoverned ka transmission

[blacksrjdm]

you can try overnighting a jdm ungoverned ka transmission

From Japaaaan.

[bradt]

Tire diameter will not affect your limiter, in a direct sense anyway. Your speed limiter is based on speed sensor input, which is in your transmission. It is calibrated with your factory wheels. What this means, is that when your speedo reads 85, you are probably going slower. Smaller rolling diameter means the wheels must spin faster to maintain the same speed as the larger wheels. This is called "deflection". The difference in speed is greater at higher speeds.

Stock rolling diameter is 627.0. Your rolling diameter is 608.90. A rolling diameter with a 50 series tire is 631, which is as close as you can get with a tire of that width.

But I digress,

It is entirely possible that the speed sensor is messing up. Check it out.

[simmode1]

you can try overnighting a jdm ungoverned ka transmission

You mean that $5000 one from this guy...



Thanks guys. I hope it's something as simple as an unplugged speed sensor! I had a speed sensor come unhooked about two years ago that prevented me from revving past 4000rpm. I guess I had forgotten to check that or I had hoped to have this problem fixed before I removed the sensors and clipped the speedo/ecu wire.

I'll check this today since I'll be underneath the car installing my new header, test pipe & Circuit Sports exhaust this afternoon...
Modified by simmode1 at 8:22 AM 4/29/2009

[Uberck]

^^ haha f***in hilarious. yea i remember the 240 sPeCiaLizT

[simmode1]

Ok guys, I checked my speed sensors and they are all secure. And the car doesn't have any grounding wires... However, while during my header install, my buddy pointed out that I was running really lean as evidenced by the carbon build up on my O2 sensor.

After thinking about it, I remembered that my old spark plugs had lots of carbon build up on them too when I replaced them last week. So apparently I have some kinda fuel issue, motor not getting enough gas probably.

Could this be the cause of the problem? If so, got any ideas on why I might be running lean?

[White Comet]

the easy fix woudl be an auto ecu

[simmode1]

^^^ I know the auto ecu will remove the speed/rpm limiters, but I'd rather find out what caused the problem & fix it before trying to cover it up with a mod.

Plus, if this is fuel related, I'm not sure the ecu swap would fix the problem.

[White Comet]

yeah thats why i said the "easy fix" it'll just cover the true problem