Does KPro manage engine rpm on deceleration

K-Series Programmable ECU installation questions / support issues
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kb58
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Joined: Sat Nov 28, 2009 2:53 pm

Does KPro manage engine rpm on deceleration

Post by kb58 » Mon Jul 15, 2013 7:59 am

Serial number of your K-Pro- Unsure, but purchased new from Hondata about four years ago.

- the calibration (as an attachment) n/a

- a datalog of a problem (as an attachment) n/a

- what sort of vehicle you have- one-off mid-engine turbo K24

- what sort of ECU you are using- 02-04 PRB ecu

- anything about the car which has been modified from stock which may affect the ECU. K24, 9:1, GT3071R, 8-psi, 400 hp, Church-tuned, PPG straight-cut 1-4 gears with dog engagement.

- a specific description of the problem
Difficulty shifting from first to second.

I know how dog-boxes work, allowing shifting at just about any time if you're quick enough. The PPG gear ratios are such that second gear is about 2/3 that of first, meaning that if I shift from first at 6000 rpm, second gear expects an engine speed of 2/3 that (4000 rpm) or it'll grind. So the problem is that when shifting fast, the engine doesn't have time to spin down. When the gears are forced together anyway, the engine is instantaniously forced to drop from 6000 rpm to 4000 rpm, with a very impressive BANG!

When driving on the street (shifting "casual"), after coming out of first gear I have to wait in neutral for about one second until the engine spins down from 6000 rpm to 4000 rpm in order to have smooth gear engagement. My question is, does KPro manage engine speed in any way as it spins down? Is there a mode that I can turn off that will let the engine spin down faster?

Below is a datalog during a 0-60 mph run, and what jumps out at me is how engine speed is literally a series of straight lines. I'll make a few more plots when reving the engine in neutral, but it does look as though the ECU is "up to something."

[img]http://www.midlana.com/Diaries/Current/0_60_time1.JPG
[/img]
Mid-engine K24 turbo Locost, http://www.midlana.com

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Hondata
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Re: Does KPro manage engine rpm on deceleration

Post by Hondata » Mon Jul 15, 2013 9:33 am

The only thing the ECU controls is the idle valve, which it opens slightly about 500 rpm above idle to prevent stalls. You can hear this on a street car with an intake.

The nature of a clutchless shift is that the dog/synchro will slow down the engine rather than the clutch, which is hard on the dogs. It is hard to tell from the datalog if the engine is taking longer then normal to slow down. The big ratio change from 1st to 2nd doesn't help either. Make sure that throttle closes fully and the throttle plate seals correctly.
Hondata

kb58
Posts: 81
Joined: Sat Nov 28, 2009 2:53 pm

Re: Does KPro manage engine rpm on deceleration

Post by kb58 » Mon Jul 15, 2013 6:22 pm

Hmm, okay, that's what I figured. I'd think that if there was a leak in the inlet it would cause a high idle. I have the IACV enabled, which works fine except for an odd occasional surge in idle rpm (a couple 100 rpm) which lasts a couple seconds, then it'll settle right back.
Mid-engine K24 turbo Locost, http://www.midlana.com

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Hondata
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Re: Does KPro manage engine rpm on deceleration

Post by Hondata » Tue Jul 16, 2013 6:32 am

That little surge, which you probably find about a minute after a cold start, is the ECU VTC cleaning procedure.
Hondata

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