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Old 12-05-2002, 08:24 AM   #1 (permalink)
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MAP sensor sensing boost

Say on a V-AFC...how high can you + the air flow before you throw a CEL? On a 5th gen prelude?

I'm trying to compensate for different size injectors, but I don't think the stock map sensor signal is going to let me do that...I think +22 across the board was what I was going to have to go with....too high I think.

Anyone?
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Old 12-05-2002, 11:35 AM   #2 (permalink)
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People usually need to set the V-AFC to a negative setting when using it to compensate for a different (typically larger) injector. Why do you need to use positive settings?
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Old 12-05-2002, 11:55 AM   #3 (permalink)
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Quote:
Originally posted by Obsidian7
People usually need to set the V-AFC to a negative setting when using it to compensate for a different (typically larger) injector. Why do you need to use positive settings?
That's the V-AFC hack.

This a N/A problem but you guys would know. I have an ecu tuned for 370cc injectors, but I want to get it to run on a 290cc injector.

See my problem? Injector pulse widths are small, so I need to tell the ecu to dump more fuel to make up for the smaller injectors...
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Old 12-05-2002, 12:13 PM   #4 (permalink)
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I could only go to +5 on the VAFC before the computer would freak out. This was when I was N/A.
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Old 12-05-2002, 01:40 PM   #5 (permalink)
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Ahh.. I came *this* close to asking if you were running smaller injectors, but I thought "There's no way he's running *smaller* injectors!"

What about picking up a set of 440cc DSM injectors? (about $50-$60 used on www.dsmtrader.com)

You can even get the injector clips from Summit Racing (www.summitracing.com, part number MSD-2400).

Then you can actually do the V-AFC hack and all should be good.
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Old 12-05-2002, 01:58 PM   #6 (permalink)
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Quote:
Originally posted by Obsidian7
Ahh.. I came *this* close to asking if you were running smaller injectors, but I thought "There's no way he's running *smaller* injectors!"

What about picking up a set of 440cc DSM injectors? (about $50-$60 used on www.dsmtrader.com)

You can even get the injector clips from Summit Racing (www.summitracing.com, part number MSD-2400).

Then you can actually do the V-AFC hack and all should be good.
No you're missing the point. I have 370cc injectors. A guy wants to run the ecu I had programmed on his 290cc injectors. This is not a turbo.

I suppose he could do the V-AFC hack...but perhaps he should just get injectors. But he's trying to use my ecu so he can get rid of the v-afc and sneak within race rules...
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Old 12-05-2002, 02:00 PM   #7 (permalink)
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Quote:
posted by Obsidian7
You can even get the injector clips from Summit Racing (www.summitracing.com, part number MSD-2400).
Can I use these clips with p&h RC 550's ?
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Old 12-05-2002, 02:09 PM   #8 (permalink)
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Quote:
Originally posted by Satan_SRV


No you're missing the point. I have 370cc injectors. A guy wants to run the ecu I had programmed on his 290cc injectors. This is not a turbo.

I suppose he could do the V-AFC hack...but perhaps he should just get injectors. But he's trying to use my ecu so he can get rid of the v-afc and sneak within race rules...
How am I missing the point? Your computer is programmed for injectors larger than the ones in the car that you want to run the computer on.

Result: It will run lean.

Fix: Get properly sized injectors.

Cheap Fix: Get cheap DSM injectors and use the V-AFC that's already there to dial it in.

Possible Cheaper Fix: Bump up the fuel pressure with an adjustable FPR (AEM?).
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Old 12-05-2002, 02:30 PM   #9 (permalink)
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Quote:
Originally posted by Obsidian7


How am I missing the point? Your computer is programmed for injectors larger than the ones in the car that you want to run the computer on.

Result: It will run lean.

Fix: Get properly sized injectors.

Cheap Fix: Get cheap DSM injectors and use the V-AFC that's already there to dial it in.

Possible Cheaper Fix: Bump up the fuel pressure with an adjustable FPR (AEM?).
Okay you're with me

Problem is he can;t use an FPR it's too obvious, unless you can modify a stock fpr to flow like 55psi?

I'm worried that at 440cc they will choke at the low rpms...I want the car to run smoothly...

Hmm maybe I'll just get the whole thing reprogrammed for 290's...

this 22% drop in injector size is difficult to overcome...arrgh...
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Last edited by Satan_SRV; 12-05-2002 at 02:40 PM.
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Old 12-05-2002, 02:45 PM   #10 (permalink)
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Why 440s? If the ecu is tuned for 370s, and he decides to resolve the problem with different injectors, shouldn't he get 370s?

Satan, you have PM concerning the reference voltage.

Last edited by sharkcohen; 12-05-2002 at 03:02 PM.
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Old 12-05-2002, 03:17 PM   #11 (permalink)
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I only thought of the 440cc DSM injectors 'cause they're cheap, readily available, and would work with what was already there (V-AFC).
Finding a set of 370cc injectors would definitely be the cleanest fix, but probably not the cheapest... plus there's a little room to grow later on if plans change.
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Old 12-05-2002, 03:19 PM   #12 (permalink)
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True, true dat.
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Old 12-05-2002, 04:10 PM   #13 (permalink)
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The only way out is 370's if he wants to get rid of the v-afc...thanks for the input guys.
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