Bucking TVS at Throttle Tip In

[ckendri]

Hey all, maybe I just can’t shift, but I figured I’d ask the question anyway. I have a MT-82 car with a VMP blower on a 79mm pulley and E85. It’s not a crazy setup. However, after shifting and re-applying the throttle under medium acceleration, my car seems to buck a little. Has anyone experienced anything similar? I really don’t feel it has to do with shifting, but I could be wrong. I feel it is more engine related, but it’s inconsistent. Should I datalog for my tuner? I just don’t want to bother them if it’s my fault. Any advice would be appreciated.

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[Roh92cp]

I know how you feel, and this has been an issue since Whipple install and made worse when I went to aftermarket clutch. Clutch spring removal helps a little, but like you very inconsistant in getting a smooth slip engagement from gear to gear. Makes me feel at times like I don't know how to shift gears, and I've been driving standards for 30 years. I'm always trying to concentrate on a smooth clutch release, more rpm and fast shift seems to help achieve this seems keeping the rpm high (idle hang) helps. This has always bothered me and again it's made worse with aftermarket clutch that is grabby with shorter engagement stroke.

 

[ugstang17]

Initially sample the E85 where you are buying it. Could be a bad batch. it happens. Also test the fuel in the tank if you have means.

If the car has been running on the existing plugs for more than a year on E85 it may be a good idea to replace them or at least pull and read them and check the gap to make sure it complies to your tuners specification. If you don't know how, take photos and provide them for assistance. Also clean the MAF and TB and see if that helps. Last you may wish to swap the fuel filter as well since you are running E85...again depending on mileage and how long the setup has been on the car which so often is failed to be mentioned on forums by people seeking help.

Last, get with Justin and/or Joe at VMP and get their feedback. Those guys have been very good to resolve issues if it is in the tune. All tuners appreciate effort such as that which I have mentioned prior to calling them and blaming their tune. Assuming this setup has been on the car and running correctly for months I encourage you to attempt any or all of the following above prior to reaching out to them.

All of this is assuming it isn't driver related, as you stated, though if the clutch is engaged and this is happening I would not be suspect of that.

 

[ckendri]

Thank you for the feedback so far. Yeah, the last thing I want to do is blame the tuner. Many of these tuners have tuned thousands of cars, so I want to check everything I can before I go to them. I noticed this about 2 weeks after going to E85 on a brand new Fore system (new filter as well). Obviously I got a tune at the same time, so that is where isolating the problem is hard. The clutch is fully engaged, and it does not happen at light throttle or WOT. It’s where I go back in to it about half throttle. WOT screams and “normal” driving is fine. It did not do this on my 85mm pulley and 91 octane, and I had the same clutch. Not saying I’m anywhere close to the world’s best stick driver, but I have driven a few.

I will check my filter and test my fuel. I am going to be pulling the engine apart a bit as I do my OPG project, so it will be a good time to check plugs. I only have 7k miles on the plugs, and 1500 of those are on E85 (3 months). If anything else comes to mind, feel free to post more.

Thanks!

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