-   OpenGauge / MPGuino FE computer (
-   -   Peak and hold injector fix done? (

wagonman76 09-12-2009 08:09 PM

Peak and hold injector fix done?
I was wondering if there is any official fix for peak and hold injectors for the mpguino? Or if it is even possible? I know it was being talked about for awhile. I am thinking about putting a mpguino in the little 91 Cavalier, 4 cyl TBI. I am pretty sure it has peak and hold injectors.

Christ 09-12-2009 11:55 PM

Peak and Hold require a resistor box, right?

Can you swap them out for internally resisted (saturated) injectors? I've done this on 88-91 Civic/CRX by using 92+ injectors to get rid of the resistor box... makes the underhood area that much cleaner.

dcb 09-13-2009 12:01 AM

I think they came in several flavors.

Someone with peak and hold needs to try this circuit (and adjust inj delay to account for optoisolator lag, and maybe trigger direction) and report back

tt460 07-12-2011 11:01 AM


Are you taking injector offset into consideration? I did not see anything in the setup where you require a user to input the injector offset... Taking that value into consideration may help increase your accuracy in Peak & Hold injectors as well as some other more common modern injectors like high volume flex fuel injectors that have more radical injector offsets.

To engine calibrators, this value is critical in accurately predicting actual fuel mass injected when dealing with different fuel injectors on the same engine. Likewise, I would think it would be mandatory to accurately calculate fuel consumption when monitoring the injector input.

dcb 07-12-2011 11:39 AM

I think this is what you mean, Injector DelayuS
it is a value that is defaulted to 500 micro seconds and is subtracted from every injector pulse to get the accuracy within the 1% range on most cars I've seen. It is the difference between the electrical signal and the actual starting/stopping of fuel flow within the injector.

I attempted to quantify the value with the additional delays imposed by this particular optoisolator here by adjusting it till I got back to the original fuel consumption readings with my bench tester.


Originally Posted by dcb (Post 106855)
...I would say make injUS delay at least 1000, or if you are coyotex, just dial it in with that diagnostic port :)

msc 07-13-2011 02:19 PM

There are two types of peak and hold drive circuits. One has a series of pulses and the other uses an analog circuit to control the hold. The pulsed type can be addressed with a retriggerable one-shot timer. The liner type is more difficult but there are ways to do it.

Your biggest issue is TBI. All the TBI systems I have looked at use two injectors and both need to be monitored to get an accurate measure of fuel usage. Any attempt to calibrate a system that only monitors one injector will result in endless frustration because it will not be consistent. Since the MPGuino can only monitor one injector you are unlikely to get satisfactory results.


dcb 07-13-2011 02:26 PM

Any clues as to how the fuel is divided between the injectors? I ask because the guy who reported the issue and worked on the project and a fix and who has substantial credibility (and an old astro van) did not indicate a problem with monitoring one injector vs two:

FYI there are some with single injectors on smaller engines.

msc 07-13-2011 03:04 PM

Other then not proportionally and it probably varies from one manufacturer to another I don't know much detail.

There are some details in this thread


All times are GMT -4. The time now is 06:41 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright