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3k flat spot and 3-stage rev limiter issues with #224/2K


turboren
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Galant VR-4 org Post #: 821957 posted 08/19/09 12:06 PM     Remind Me!  Send Private Message   Edit Post      
Been a while since I've been on the board, but I've been pretty busy this summer workin on my cars. Anyway, I have a couple issues with #224 that I'd like to see if anyone can help with. First, the relevant specs:

Blaha hacked 1g mas
Big 16g (or evo3, can't remember offhand, and I'm not near the car)
really big fmic, 2 1/4" in, 2 1/2" out (I think)
greddy type r bov, open vented (recirc line not made yet)
2g tb elbow
FIC 650's
2g exh mani
evo3 O2 housing
3" ss exhaust with magnaflow muffler, no cat
Keydiver chip set up for above, plus 3-stage rev limiter (4500 rpm default), 7800 top rpm
SAFC set up: throttle 30% low, 80% high; fuel on low -5% at 1k, -5% at 2k, -3% at 3k

Ok, so problem #1 is that the rev limiter sometimes work and sometimes doesn't, meaning sometimes I get 4500 rpm, and other times I get 7800. I haven't been able to narrow down when I get what rev limit (can get either rev limit while moving or standing still, with clutch in or out), but I'm sure there must be something I'm doing, or not doing, to make it do that. I haven't done the clutch wire mod, so I don't know why I would ever get the 7800 rev limit, but I don't totally understand how that circuit works anyway.

Problem #2 is that there is a pronounced flat spot, and occasional bucking, at part throttle from about 3k to 4k rpm. If I floor it, though, the engine responds fine. I logged the event, but haven't reviewed the logs yet, so I'm not sure what is going on, but I didn't notice any knock of loss of Hz at the time. Fuel trims from the logger say about 82% low, 82% mid, and 93% high.

I'll try to download the logs tonight or tomorrow and see if I can post them.

Any ideas greatly appreciated.

Thanks,

Ren

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Rausch Galant VR4.org Moderator
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Galant VR-4 org Post #: 821979 posted 08/19/09 01:27 PM     Remind Me!  Send Private Message   Edit Post      
I *think* problem #1 may be related to the VSS. If I remember correctly, you get the lower limit when teh ECU sees the car is not moving. I know the clutch switch is involved here too, but if it's not wired up for that mod I'm not sure how exactly. Forgive me, as it's been forever since I hooked any of that stuff up, I'm sure Jeff would be able to elaborate with the most accurate info.

Edit: The clutch wire mod should not affect the 7800 rpm limit though.



Rance lives here...
Founder of Sold out to BMW Cru, then sold out there too.



Edited by Rausch (08/19/09 01:30 PM)

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belize1334
well bread and nobly conceived
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Galant VR-4 org Post #: 822109 posted 08/19/09 09:32 PM     Remind Me!  Send Private Message   Edit Post      
The rev limiter issue is because the ecu isn't getting a signal from the vss so it thinks that you're sitting still all the time. I had the exact same issue and it turned out not to be the switch itself (located in the instrument panel) but rather a short in the wiring between the vss and the ecu. Once I determined that the sensor was working fine I just sent a new wire all the way from the vss to the ecu and voila...problem solved. Also, for your edification, there are other symptoms of a bad vss. For one thing, your variable speed wipers aren't variable speed anymore cause they think the car is sitting still all the time so they don't adjust for your vehicle speed. The other thing is that the car may be prone to bogging the engine as you approach stop signs. Normally the ECU knows that you aren't giving it any gas and that you'll be using the brakes (which draws vacuum from the intake manifold) so it keeps the RPMs at about 1k until you come to a complete stop. If the ecu doesn't get the speedo signal it doesn't know that you're slowing down so it doesn't keep the RPMs up. The result is that it's idling at about 750rpm when you apply the brakes and the engine bogs.



Roger B. Scott
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toybreaker Galant VR4.org Moderator
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Galant VR-4 org Post #: 822140 posted 08/19/09 10:40 PM     Remind Me!  Send Private Message   Edit Post      
^^^ Good info!

Also, one other "tell" for a defunct vss is a non-operative cruise control.



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turboren
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Galant VR-4 org Post #: 822852 posted 08/22/09 10:25 AM     Remind Me!  Send Private Message   Edit Post      
Cruise and wipers work as they should (well, cruise hunts somewhat, rather annoying), and I haven't noticed any bogging while coming to a stop. As I said earlier, though, the low rev limit thing doesn't happen all the time, and it actually hasn't happened at all in the past couple hundred miles.

Still having problems with the flat spot, though.

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turboren
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Galant VR-4 org Post #: 824818 posted 08/28/09 04:54 PM     Remind Me!  Send Private Message   Edit Post      
Turned up the boost and it just bogs at anything over 10psi. Turned it back down until this is fixed. I haven't made up that clutch wire yet, either. Can I just use some off-the-shelf diode for that? Doesn't look as though the one pictures in VFAQ is very big.



1078/2k-sold, 733/2k, 224/2k, 1571/2k (AMGVR4)-sold
74 Mazda REPU; 87 CRX Si; 95 Ford Aspire (x2); 92 Laser RS AWD; 94 GMC Sonoma; 96 Miata M ed (turbo); 02 Vespa ET4 150 (new daily)

Posts: 538 | From: Norfolk, VA | Member Since: 08/20/03 | IP: (205.56.129.195) | Report this post to a Moderator

belize1334
well bread and nobly conceived
1334/2000


Galant VR-4 org Post #: 824834 posted 08/28/09 05:29 PM     Remind Me!  Send Private Message   Edit Post      
I wouldn't worry about the clutch wire till everything else is working. The no-lift-to-shift shouldn't interfere with anything else if you just leave the wire off. You'll still have the basic launch-control feature and it'll simplify the diagnosis for your intermittent rev-limiter problems.



Roger B. Scott
'91 Belize Green

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turboren
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Galant VR-4 org Post #: 825515 posted 08/31/09 07:33 PM     Remind Me!  Send Private Message   Edit Post      
Well, I just found out that I don't have NLTS on that chip anyway, which seems to make even less sense to me. Also discovered that my base fuel press is 40psi with the vac hose on, 44 with it off (fuel press solenoid still in use).

Posts: 538 | From: Norfolk, VA | Member Since: 08/20/03 | IP: (70.160.227.250) | Report this post to a Moderator

turboren
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Galant VR-4 org Post #: 828852 posted 09/11/09 10:41 PM     Remind Me!  Send Private Message   Edit Post      
Here are some logs that I took when this occured. Maybe I'm just not that savvy with MMCd, but I don't see anything that stands out as something wrong:

click

click

click

From what I can gather, this seems to happen between abnout 15% and 30% throttle.

Anybody got any ideas?

Thanks,

Ren


Edited by turboren (09/11/09 10:44 PM)

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Hertz Galant VR4.org Administrator
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Galant VR-4 org Post #: 829091 posted 09/12/09 10:23 PM     Remind Me!  Send Private Message   Edit Post   
I had a similar problem go away after discovering boost leaks that I swore did not exist. Pressure test often.



Ryan Hertz

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