20v 4age Rev limit

[mulkers]

My bro has recently gotten an 86 with a 4age silvertop 20v, with what i assume is a pretty conservative rev limiter at 7000rpm. It is stockish, save for larger injectors, an EMS ecu, MSD outboard coils, ram tubes, and an exhaust.

I am after the factory rev limit, and recommendations for a higher rev limit, as it seems very restricted, and still pulls very hard.

Cams and head work will be done shortly, and the limit will be changed then, so i was enquiring as to what was a safe, and higher rev limit.

Cheers

[Roundy]

i might be wrong but i think the rev limit is somewhere in the vicinity of 7800 - 8000

[TooF]

the n/a 16v will happily spin to 8k im pretty sure the 20 is around the same,

[The Last Streetfighter]

My 20V ST rev limits at just over 8k bog stock.

Not sure what it revved to before the speed sensor fix as I did that at the same time I got the Tacho cluster.

[adamaw11]

I think mine used to limit at 8200, but my tacho might have been slightly off all along. my 16v also seemed to show just over 8k iirc

I reckon 8500ish would be an acceptable limit with cams and headwork.

[Sam_Q]

from what I hear its 7500 without a speed sensor input and 8000 with

[psychofox]

With a stock engine I woudn't bother taking it much over 7500rpm. It's certainly not making any more power....max power on a stock ST is around 6800-7000rpm Set the rev limiter to 8000 and don't worry about rod bolts letting go.

[-GT-]

Mine climbs all the way to the 7800 limiter, definately past 6800-7000. Fletcher, surely yours did to?

Blacktops are 8200rpm.

But why does it have bigger injectors in it if it's stock? Anyway, 8000rpm would be suitable, for after cams and headwork i remember someone with racing experience saying in a thread on here that late model 4age stock bottom ends should be fine for 8500rpm with just a good balance and cleanup. I think it was that they started stretching stock rods at about 8800-8900?

Don't take that as anymore than a recollection of someone else's opinion though, i can't find it now, but i'll keep looking.

[The Witzl]

A correctly wired silvertop 20V 4A-GE has a factory rev limit of 8200rpm.


Without the SPD signal to the ECU (speed sensor), the rev limit is reduced to 7800rpm as the ECU thinks you are "free-revving" the engine.


I know this as i tested it personally on Finney's 20V once i finished the conversion.

[JP]

I've had the same experience as Witzl on both the AE101 and AE111 20V swaps I've done.

You get a premature revcut with the speed sense wire disconnected, with it connected it revcuts around 8200

[-GT-]

Actually i think you've told me that before Karl, sorry guys
Can you remember which wire that is? ie colour, where it comes from? Anything to help me find it easier when i go to connect it?

[The Witzl]

Purple wire with a white trace. (V-W)

All of the EFI AE92 cars already had this wire going to their factory ECU (you'll find it in the area behind and below the ashtray).... so it's just a matter of attaching this wire to the 20V ECU, and Bob's your mother's brother.


Look.. i even have a picture!! This is the original 16V 12-pin ECU connector, which i am re-pinning to suit the 20V ECU pinouts for same connector. The SPD signal will be on this connector, as clearly seen.

[-GT-]

So it's coming down from the dash/speedo cluster? Sweet, thanks Karl.

[The Witzl]

yup
Coming down from the dash

[Blind Kid Seeks]

just digging up an old thread for fun.....

Witzl... can you confirm, my AE93sx did have the purp/white wire at the ECU, that now i have plugged my Purp/white SPD sense wire into the 20v ECU in the SPD pinout, that all is well and should now be recieving a signal to raise the RPM cut...

perhaps my Tacho is out.. still seems like theres a 7800 rpm cut.....

will have a closer look at the wiring again.