rev limit or something else?

[hoveringuy]

Help!

I refreshed the motor in my e30 and now I can't get it to rev over 6000rpms. It feels like it's hitting the rev limiter, even though it's set to 7000.

If I re-set the limiter to 4000 it will hit the limiter at 4000, but when I set it to 7000 it still won't go over 6k.

I'm not maxing my injectors.

The only thing different with this motor from the other one is that I'm using a Toyota Supra igniter box, I'm not aware of any reason the Toyota igniter would limit me to 6000.

Am I missing something in my configuration to cause this?

Attached .MLS shows me bouncing off 6000 in first gear.

Thanks!

[CRSTune]

Try backing off the dwell to around 2.2ms and see if it improves. Toyota ignitors are smart ignitors and will do that when charged too long.

[hoveringuy]

Try backing off the dwell to around 2.2ms and see if it improves. Toyota ignitors are smart ignitors and will do that when charged too long.

That solved it!

I've heard about the smart dwell control but thought it would just limit the charge time, not cut it off completely. If you can explain why/how the smart dwell control was doing it, that would be great!

[CRSTune]

[That solved it!

I've heard about the smart dwell control but thought it would just limit the charge time, not cut it off completely. If you can explain why/how the smart dwell control was doing it, that would be great!

Glad to hear it!

Smart ignitors have a built in dwell limiter. Some use a flat timer (cannot charge longer than X ms) while others will use a max duty cycle and "smart charge" the driver. When overdwelled, they go into Soft Shut Down (SSD) mode which discharges the driver internally to prevent overcharge.

[hoveringuy]

At 6000 rpms each plug fires once every 20ms.

If the smart dwell limit based on a max duty cycle,
3ms out of 20ms is only 15% duty.

[CRSTune]

At 6000 rpms each plug fires once every 20ms.

If the smart dwell limit based on a max duty cycle,
3ms out of 20ms is only 15% duty.

You can set it to constant duty and see how it performs. I've used 10%-15% before using an IS300 ignitor which I had believed to be based on constant duty. The only problem was that on a subsequent car, those same settings caused issues around idle due to overcharge. This was done on a VVTI 2JZ at high boost so dwell was an important factor in allowing for larger spark plug gaps while preventing spark blow out.

As a compromise between the two, I had intended to use constant dwell using a dwell duty table and no battery voltage correction (or at least no increase to dwell based on voltage). It would be set to a constant dwell number and slowly decreased at higher RPM as if keeping a constant duty cycle. I never did get a chance to test it though.

For now though, if the engine performs well at 2.2ms, I would just leave it as is.