Whipple 2.9 Gen3 - Slight hesitation

moncho

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Wanted to share a situation I'm currently experiencing with my recent Whipple G3 install. I'm having an issue where I get a partial boost hit (2-3 psi) during moderate acceleration. This causes a slight hesitation/power loss and momentary lean condition. Now if I feather the petal I remain in vacuum and the car accelerates as expected without hesitation. At 1st this happened @ idle and through a tune revision it moved up to about 1800 rpm. When you mash the petal it responds real well, seeing 16-18 lbs of boost from -16.5" of vacuum. Keep in mind I'm at elevation of 5280'. The tuner tells me I have an over active bypass actuator & I'll need a bypass restricter (aka nitrous jet) to calm it down. This remedy however is known for configurations with comp cams that result in lower vacuum, I'm stock in this regard. I did have a second set of eye's (reputable tuner) look @ the tune and he confirmed it was spot on. He showed concerned however on the plugs I have on the car (NGK Tr7IX). He said the plugs I'm running are very cold and could cause spark blow out. He recommended TR6's, so I swapped them in yesterday - will try and take it out this evening. Whipple is looking into it but hasn't given me a possible solution. It may possibly be in the form of the bypass restrictor jet or a different bypass altogether. I did record several video's of the bypass actuator, from engine off (bypass closed) to engine on (bypass open). Whipple states it's operating correctly all the way down to where the plunger transitions from closed to open on startup & closed when the engine is turned off.

Here's a link...

The '13 folks don't appear to have an issue to the best of my knowledge?

However there is a current post on the GT350 forum with essentially the same issue as mine...

Here's the link...Thanks @SCGallo2 for letting me know of this!

Anyone running one of these with a similar configuration as mine w/o this issue?

I'll upload 3 files - log0022_Hesitation_R2 was a revised tune, log0025_Hesitation_R3 was also a revised tune but adjustments were made for the hesitation, which moved it up to about 1800 RPM instead of idle RPM. The last log is a 3rd gear pull/WOT that shows things are in order on the upper power band.

Maybe a good idea to hold off on one of these until it's sorted out.

Thanks!
 

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69b302

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I did not see open loop flag in your logs files. Your trims look to indicate you are not going open loop, when this condition occurs. You might want to bump your TP count thresholds down, so you are open loop when into any boost. The newer PCMs are always closed loop, but the older cars go(or should go) open loop when into any power, since the O2s are narrowband. My 0.02
 

RBB

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The remedy for cars with cams that are making low vacuum is a low vacuum bypass....has a much lighter spring. Not sure why you'd need one of those if you're not cammed and making the normal amount of vacuum, unless your high elevation is causing you to make low vacuum. Put a vacuum pump on the top port (with the line going to the passenger side of the blower) and see how much vacuum it takes to close your valve. Here's a link to the light spring bypass.

https://www.teambeefcakeracing.com/whipple-bact-1015.html
 

69b302

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I looked at the first log and the last log(good WOT). Your STFT should read your configured open loop lamba, when the car is in open loop. This is the case for your good WOT pull, but not for the log when you have the hesitiation.
 

moncho

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@RBB without removing the blower it's virtually impossible to check the vacuum it takes to open the actuator. You did mean open the bypass correct? It rests in the close position when car is off. I'm getting -16.3" of Hg, the stocker was closer to -19 -> -20, elevation may play a roll in this somehow. From the video's I took the opening of the actuator is instantaneous when car starts. The log files appear to show the transition @ about 0" of Hg.
 

moncho

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I did not see open loop flag in your logs files. Your trims look to indicate you are not going open loop, when this condition occurs. You might want to bump your TP count thresholds down, so you are open loop when into any boost. The newer PCMs are always closed loop, but the older cars go(or should go) open loop when into any power, since the O2s are narrowband. My 0.02

I looked at the first log and the last log(good WOT). Your STFT should read your configured open loop lamba, when the car is in open loop. This is the case for your good WOT pull, but not for the log when you have the hesitiation.

These are great observations for sure. You make a good point on the difference between the old & new PCM's. Something I was thinking about since it appears the '13/'14 folks aren't having this issue. Now I need to communicate your findings to the tuner. You'd think this would standout for them since this is what they do.

Thank you sir!
 

RBB

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@RBB without removing the blower it's virtually impossible to check the vacuum it takes to open the actuator. You did mean open the bypass correct? It rests in the close position when car is off. I'm getting -16.3" of Hg, the stocker was closer to -19 -> -20, elevation may play a roll in this somehow. From the video's I took the opening of the actuator is instantaneous when car starts. The log files appear to show the transition @ about 0" of Hg.
Yeah, I meant open. If you're around 16" you should be fine at idle, which it appears you've verified. I don't know why you'd be going into boost at part throttle. I can tell you, though, that I just put a low vacuum bypass on my car and it exhibits the same type of behavior you're describing. My data logs look fine and I'm not having any lean spikes, but sometimes when I'm in part throttle situations and my vacuum gets low enough to release the actuator (4") I get a surge into boost. It's almost like an on/off switch....the stock bypass never acted like that.
 

MastaAce03

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The TR7ix is an appropriate plug for your boost level.


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TBCobra

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Maybe in the meantime, post some pics of your car. :)
 

moncho

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^Sure...

IMG_6320.JPG whip_29_g3.jpg IMG_5774.jpg IMG_5775.JPG
 

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