502 Ram Jet w/Holley Commander

[TopRat]

Are any of you guys running a 502 Ram Jet with a Holley Commander ECU? My issue is a hunting idle that I can't seem to tune out of it. Any suggestions would be appreciated.

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[andrewb70]

Are any of you guys running a 502 Ram Jet with a Holley Commander ECU? My issue is a hunting idle that I can't seem to tune out of it. Any suggestions would be appreciated.

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I am not sure how many have done this but I see no technical reasons why this would not be a simple swap.

Andrew

[pushrod243]

the hunting at idle is prolly more a charactaristic of the ramjets throttle body than anything else. I have a Fast xfi on my rj502 and it stills is touchy when returning to idle. A gm tech at sema told me it had to do with the isc motor reacting too slow. And the gm was working on a fix. Not sure if they ever fixed it. mine is better with the xfi but still kinda annoying

[andrewb70]

the hunting at idle is prolly more a charactaristic of the ramjets throttle body than anything else. I have a Fast xfi on my rj502 and it stills is touchy when returning to idle. A gm tech at sema told me it had to do with the isc motor reacting too slow. And the gm was working on a fix. Not sure if they ever fixed it. mine is better with the xfi but still kinda annoying

I am sorry but the GM tech must have been one of those marketing guys. LOL The Ram Jet uses the same throttle body as an LT1. It is all in the tune and should definitely be able to tune it out with the XFI or the Commander.

Andrew

[TD509EFI]

Andrew,

Are you having trouble with the RamJet MPFI ECM and you want to switch to Holley C950, or are you having trouble with the Holley?

Generally, if hunting is a problem with any setup and you're sure you've dialed in you idle parameters, then the problem can often be caused by poor grounds, offset voltages due to different grounds, or noise getting into ECU from ignition sources or WB O2 controllers. Another problem can be noise getting into the IAC leads from ignition or alternator.

If you already have the C950 ECU , further help can be found at the chevytalk.com site in the EFI sub forum toward the bottom of the page. Doug Flynn, who worked on the Holley setup, is the moderator and often replies to problems. A really great guy to deal with!

By the way, I love your setup!! That's sweeeeet! I'm in the process of installing a 509 BBC EFI with a custom plenum and a Holley C950 in my 79 Z and I'm working on a dual air intake that's very similar to yours. Did you put the air filters on the other side of the core support? Thats where I'm putting mine.

I'd love to see more pix of your car. Hopefully, I'll be starting assembly of mine by late Spring. You're much further ahead than I am.

John

[andrewb70]

Andrew,

Are you having trouble with the RamJet MPFI ECM and you want to switch to Holley C950, or are you having trouble with the Holley?

Generally, if hunting is a problem with any setup and you're sure you've dialed in you idle parameters, then the problem can often be caused by poor grounds, offset voltages due to different grounds, or noise getting into ECU from ignition sources or WB O2 controllers. Another problem can be noise getting into the IAC leads from ignition or alternator.

If you already have the C950 ECU , further help can be found at the chevytalk.com site in the EFI sub forum toward the bottom of the page. Doug Flynn, who worked on the Holley setup, is the moderator and often replies to problems. A really great guy to deal with!

By the way, I love your setup!! That's sweeeeet! I'm in the process of installing a 509 BBC EFI with a custom plenum and a Holley C950 in my 79 Z and I'm working on a dual air intake that's very similar to yours. Did you put the air filters on the other side of the core support? Thats where I'm putting mine.

I'd love to see more pix of your car. Hopefully, I'll be starting assembly of mine by late Spring. You're much further ahead than I am.

John

I am not having issues, TopRat is. he has a stock Ram Jet and is having idle issues. He was asking about swapping the RamJet eleconics for the Holley since the Holley can be tuned while the RamJet can't. Doug F comes here a lot as well.

Andrew

[tomspo04]

Are any of you guys running a 502 Ram Jet with a Holley Commander ECU? My issue is a hunting idle that I can't seem to tune out of it. Any suggestions would be appreciated.

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TopRat, Where did you get that split intake tube, if you don't mind me asking?

Thanks, Tom

[rockdogz]

TopRat, Where did you get that split intake tube, if you don't mind me asking?

Thanks, Tom
LOL, hey I wanted something similar to that too, dammit!!
Looks good, BTW

[TD509EFI]

Sorry Andrew, put the wrong name in at the top of the post. My apologies.

TopRat, have you had any luck with the hunting idle?

John

[andrewb70]

Sorry Andrew, put the wrong name in at the top of the post. My apologies.

TopRat, have you had any luck with the hunting idle?

John

No problem.

Andrew

[aggressive male]

I don't have a 502 ramjet or a commander 950 but I do run a holley pro-jection 2D and I had the problem of a hunting idle once. I fixed it by testing and adjusting the throttle position sensor. Do you have the papers that came with yours? Do you have a digital voltmeter? Turn the ignition on and test between the blue and black wire and make sure it is between .63 and .65 volts at idle and at full throttle it should be between 4.5 and 5 volts. Open and close the throttle slowly while looking at the meter to make sure there are no dead spots in the tps.

[TopRat]

Thanks everyone for the reponses, just to clarify I'm running the GM Ram Jet intake on my 502. The throttle body is an Arizona Speed & Marine 1300cfm mono blade not the original. I also removed the stock GM ECU and replaced it with a Holley Commander Pro unit, I can obtain an idle but it hunts around by about 100rpm or so and I can't seem to tune it out. I have tried many IAC and timing settings but the idle still hunts around.

John, thanks for the tip, I'll also try the forum at chevytalk.com maybe someone there will have a similar setup. The engine runs great otherwise...I'm just a bit picky about the idle quality.

Tom, the twin intake was designed by me and fabricated by a local race and rod fabricator here in Boise, ID "Qualifab". the intakes are positioned behind the headlights with dual K&N filters. Moving the air intakes to behind the headlights instead of the filter directly behind the radiator dropped the intake air temp by 80 degrees or more depending on ambient air temps.

As far as my idle issues, I've tried many settings with the C950 on the IAC settings with Proportional, Integral and Derivative terms along with Idle Spark Control on and off but still can't obtain and acceptable idle.

Thanks, Alex

[Doug F]

You might try opening the throttle plates up a little bit and "overiding" the IAC slightly.