Top speed limiter

[BruceBe]

Folks,

We've had the race-car on track again for testing, and the new (used) engine seems to be holding up OK. The clutch is also holding up fine.

Interestingly, we're hitting a top-speed limiter at about 5500rpm in 5th gear (running the ZF 5-speed with a 1:1 5th gear). This is with a 404 ECU and a Dinan 540i chip. I see several possibilities:

1) The speed signal that I am sending to the ECU (see my other post on this) is getting "dirty" as the road speed gets high, and the ECU effectively loses the signal

2) The Dinan chip preserves the top-speed limiter

3) Some other issue

I purchased the chip used from someone on CL, and it did add power/tq in a back-to-back dyno test. It also had the original Dinan label on it, and I'm pretty sure the chip is legit. On the dyno, the car would pull to 6500RPM without issue in 4th gear, so the rev-limiting seems to be correlated with road-speed.

Does anyone know if Dinan preserves the top-speed limiter on their performance chips for the 540? Any other thoughts?

-Bruce

[Jean]

Bruce,

I wonder if calling Dinan would get you the answer ?

Also, what speed(s) are you getting in gears/what diff?


thanks!

[BruceBe]

I'll definitely give Dinan a call - the challenge is getting to someone who knows the specifics of the programming.

Since the reed switch is picking up a toothed reluctor attached to the ring gear, I don't think gear ratio is relevant to calculating road-speed. A stock 540i had a 225/60/15 tire, and with a 2.93:1 diff (a stock ratio, I believe), 5500RPM in 5th would be somewhere around 140MPH. That sounds like a reasonably high-number to limit a stock 540i.

-Bruce

[Jonsku]

Just a check, do you have correct speed-signal for ECU?

I had a problem with the cabrio that engine kept cutting out power when the road-speed went over 120-130mph but it turned out to be that I had missed the speed signal (from instrument cluster) to ECU.

Just a thought..

[BruceBe]

Just a check, do you have correct speed-signal for ECU?

I had a problem with the cabrio that engine kept cutting out power when the road-speed went over 120-130mph but it turned out to be that I had missed the speed signal (from instrument cluster) to ECU.

Just a thought..

My understanding is that a missing speed signal would cause an artificially low *rev* limit in all gears. The logic is that without the speed signal, the ECU defaults to the rpm-limit that would be allowed in *top* gear to honor the top speed limit, as set from the factory. For example: if a car had a top-speed limiter of 130MPH, and this equated to 5500 RPM in 5th gear, then the rev-limit in all gears would be 5500RPM, to ensure that the car never exceeded 130MPH. I know this is the case with the 6-cylinder cars, hence the "speed-delete" option from the aftermarket performance chip manufacturers.

In our case, we are getting full RPM (6500 +/-) in all but top gear, which makes me think that the ECU is indeed getting a speed signal, and honoring the top-speed limit that is on the chip.

It may be that we're somehow not correctly conditioning the speed signal to the ECU, but on these cars it is pretty much brain-dead simple. A magnetic reed switch closes and opens a 12V circuit. Everything I could find out about the stock dash indicates that it pretty much just passes that along to the ECU, with a pull-up resistor to minimize current flow.

-Bruce

[E30SPDFRK]

Mine stops at 6500 in 4th at 120mph. It does the accelerate-decelerate-accelerate-decelerate thing that I've seen other speed limiters do. I bought a WAR chip thinking it would eliminate the issue but apparently not.

Let us know if it turns out to be something to do with the car rather than the ECU

[Jaxx_]

Mine stops at 6500 in 4th at 120mph. It does the accelerate-decelerate-accelerate-decelerate thing that I've seen other speed limiters do. I bought a WAR chip thinking it would eliminate the issue but apparently not.

Let us know if it turns out to be something to do with the car rather than the ECU

lol isn't that just the rev limiter?

[naika]

Hi Guys,
Interesting discussion as I just finished my M62B44 OBD1 swap in my e30 and I haven't plugged the speed info yet in the cluster, therefore, my ECU goes into safety mode.

Anybody could tell me exactly where to plug the black and white wire from the M60 engine harness on the cluster?
I heard I may need the Cruise control green plug to be able to plug my speed info in it.

Any help would be appreciated.
Thanks to all you guys ;)

[g3n0cid3]

Connector C2, pin 10, wire color BU/YL on the back of the instrument cluster goes to pin 42 of the 404 DME. This is for my setup at least. See attached picture for C2 location.

[naika]

Thanks for the info
Would C2 be the speed info to the OBC?
I believe that I need to connect the speed info to Pin 14 on the engine harness from the V8 (which may actually feed the pin 42 of the 404 dme?)

I think I understand it better now.
Thanks for your help ;)

[g3n0cid3]

I’m assuming that you are using a M60B40 black label 404 DME. Pin 14 (gr/bl) DME is MAF ground, and pin 42 (blk/wht) DME is Speed signal. Run a wire from pin 42 on the DME to pin 10 on connector c2. Or the signal can be run through connector c101 pin 14 to the DME. Pin 26 of C3 (br/rd) goes to OBC with the speed signal. Here is a diagram of my cluster:

[naika]

Thanks a lot, that confirms what I thought. And it seems to I have several options then to source the speed signal.
I'm installing in the next few days, so I'll try the C2 (pin 10) , C101 pin 14 to DME and will let you guys know ;)

Thanks!

[naika]

I have another question if you don't mind.

Which wire is giving the RPM signal to the cluster from the ECU?
I need to install my pulse converter for the V8 to 4 cyl cluster and I need to install it on the wire giving the signal, but i don't have the color of that one.

Thanks again ;)

[g3n0cid3]

For the instrument cluster; connector c1, pin 7, size .5, black. And for the DME; pin number 47, black.

[naika]

Thanks a lot ;)
Now I can install my pulse divider and new cluster with speed signal :)

F.