unwanted throttle blip on decelerating

SurfDog

I have an uprev tune done at zcargarage in San Jose but am about to re-tune for high altitude driving in Colorado.

two questions (one easy one harder)

1. Do I need to retune from my present settings at warm sea level, to cooler and much altitude higher driving??? (between work at 5,500 feet and my home at 9,000 feet). I feel like the computer will adjust, but really do not know.

I could easily replace the Valet map(#3) or stock map(#2) for a mountain map.

2. I have experienced numerous occurrences of the following: While decelerating in a right fairly aggressive downhill turn (engine braking), about two seconds after the downshift (with and without SRM) I get a little "throttle blip" and lose some of my engine braking. Could this be a VDC function? It is really annoying, and (as I am usually counting on the engine decel) has me hopping on my brakes (which is inelegant and maybe a tiny bit unsafe as it always catches me by surprise)

3. (bonus question) Anybody have a good denver area tuner they can recommend??

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix

Sh0velMan

RE: the engine braking thing. Depends what RPM you're at. The engine does seem to open the throttles a little at low RPM to help keep the engine running at what it seems to think is too low an RPM for the calculated load.

I wouldn't worry about it as long as it isn't happening at 4-5k rpm or something.

Logs would be needed to see what it's doing, at any rate.

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Red__Zed

I would definitely get a new tune for the altitude.

SurfDog

That is the weird thing, it is happening at high rpm's during engine breaking.

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix

Red__Zed

Are you at a high enough rpm that you might be losing grip otherwise?

What tires are you running?

SurfDog

Stockers on dry asphalt. I'm thinking it might be a VDC thing to hold the turn... Dunno.

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix

Red__Zed

It's been cold here, and the stock tires probably aren't gripping that great. I bet the car is trying to control/prevent slip.

Sh0velMan

What RPM specifically?

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SurfDog

Yeah that is my guess too! I just didn't know the VDC could do that.

I was wondering if anybody else on the forum had experienced that type of "traction control". The first time I felt it (it happens on an off-ramp I sometimes take coming into San Francisco) it definitely felt like malfunction or poorly tuned electronic throttle kind of thing. The car is in Colorado now but I have a great off-ramp in mind to try and reproduce the conditions in another spot. I guess I'll look for the VDC light to flash at me to indicate a "correction."

The thing is, it feels like I'm pretty far from losing traction when this happens. (not on the edge of the traction circle from the feel of it) So it is pretty (overly) conservative if it really is the VDC. I guess the thing to do is try to reproduce the phenomena in straight and turning decelerations to see if it really is a traction correction.

Anybody else ever experience this?

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix

SurfDog

4-5k rpm I'd say (engine breaking)

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix

dal1307

3. (bonus answer) MAC Autosport (Welcome to MAC Autosport) I don't trust anyone else around here. Tell them that Dave with the Stillen SC Blue Slate G37 sent you (BTW, that is my car at the top of their home page).

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2008 G37s 5AT, Stillen SC, Stillen CBE, Stillen tranny cooler, DBA 5000 front/4000 rear, Stillen sways, Tein SS-P coilovers, SPC front & rear control arms, Goodridge lines

SurfDog

Thanks I just called them for a tune and 30k fluids (redline tranny/diff) yesterday. I'm hoping I like em as much as my mech in Cali!!!!!

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix

dal1307

They have definitely treated me and my ride well. When are you going in for the tune?

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2008 G37s 5AT, Stillen SC, Stillen CBE, Stillen tranny cooler, DBA 5000 front/4000 rear, Stillen sways, Tein SS-P coilovers, SPC front & rear control arms, Goodridge lines

Sh0velMan

Sounds like VVEL switchover at around 5200. If you have cipher you can log VVEL position and see there is an 'event' at around that RPM that can cause a blip of sorts.

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SurfDog

Yep! Tune, diff/tranny fluid replace and an oil cooler (with oil change of course.)

They are recommending the 25 row Stillen oil cooler.

Quoted me a bit under $1500 or so for all.

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09 6spd Berk CBE, JWT cams, ZSpeed CSC, Stillen (25 row oil, brake cooling, sways, gen3 CAI), Passport (9500ci), Quaife LSD, Z1 400 hp kit, ss lines, pads, rotors, clutch etc, Phunk's pan and fuel starve fix