Jump to content
SAU Community

Recommended Posts

Hmm, so mods are as listed in my signature. Basically changing from 1st to 2nd or 2nd to 3rd at about 6.5-7k rpm the car feels like for a fraction of a second it's starved of oxygen, and kind of jolts, then it jumps forward. It does it randomly, at different temperatures, not on every shift. Mainly when im shifting fast to.

I have a few ideas on what it could be, but i want other peoples opinions. thx

Mine does this aswell, but only when changing gears fast (it hesitates for a split second before power comes on strong).

I always put it down to the BOV not letting enough air out on gearchanges when the throttle is closed, stopping the flow of air to the engine for a split second.

That air then has to be brought back to speed once the throttle is opened after the gearchange, hence the slight hesistation before power comes on (lack of air speed initially).

I could be totally wrong though.

Fixxxer :laugh:

I was actually thinking on the contrary, that it was the BOV emptying too much air out (i.e. a leak?), that resulted in starvation after the change as the piping was refilled.

What your saying makes more sense.. maybe my BOV is on the way out, people say they are good to about 230rwkw normally

Anyone else?

Edited by 123456

A BOV doesn't effect the speed of the air on the way to the engine.

All it does is release pressure so that the blades of the turbo can keep spinning.

If you had a hose spraying water into your garden and you quickly stuck a hole in the side of it, you aren't increasing the speed of the water out the nossle.

How long since your re-map. Might wanna check out some tuning issues first.

Um about 2-3 months, and only thing i've changed since remap is the dump and a new cat, which didn't make the surging any worse, any other suggestions? Just feels like it's starved of air.. or fuel after change, could it be timing related or not?

To continue on from what I was saying before, and what I think happens is that the BOV will release pressure or 'boost' in the pipes after a gearchange.

After getting back on the gas again, the throttle is reopened, turbo shaft speed has also decreased by being off the gas (by how much I don't know), but the pressurised air that was in there just before the gearchange is gone/vented. The turbo has to then build pressure in the system, which shows up as a hesitation on quick gearchanges.

Therefore I think that a large FMIC setup with large pipes will exacerbate this problem.

Fixxxer

You are talking about turbo lag yes I noticed. Its not "stopping the flow of air" is what I was saying. If you think about it, with a less effective bov or no bov, the engine see's boost for longer, the only thing that is aided, is the speed of the impellor.

I'd be checking the AFR. You say yourself it feels like a afr issue. Thats the only way to be sure I reckon.

when you change gears quickly the bov doesn't have much time to dump air, so there isn't much of a pressure loss in the piping.

i'd possible point the finger at the boost controller. the air between the controller and the wastegate isn't able to escape fast enough, so the wastegate is still partly open when you get on the gas again, so you have less boost until the wastegate is fully shut.

Ah yeh, thats true, if changing quick it wouldnt have much time to vent.. Do you think it's worth getting a new controller then? Or are you saying boost controllers in general can cause this problem? The joint that tuned it seemed to think that they (Can't remember brand, they were $29, had a long topic.. turbosmart?) were pretty decent

Heres a dyno graph if that helps (before new CAT and Split dump)

mydynokt1.png

thx

Edited by 123456

You need to be able to change the gears with out shutting the throttle... eg Flatchange!

And inless you want things to break I surgest not doing that inless you have a ecu that will allow you to do it also...

Or buy an auto!

Other than that you proberly have a fuel issue; tuning/supply

Edited by cameron

Is that a dyno sheet for ants?

Everyone is thinking turbo lag... I don't know if he is describing that. Jolts and feels like it starved... then jumps forward, sounds like something being too rich...

I still reckon check out the AFR's and see if its gone a bit silly due to a small problem somewhere along the line.

A atmospheric BOV vents measured air to the atmosphere. Your cars air flow meter has measured X amount of air in the system which requires Y amount of fuel. When people screw around by dumping the measured air out of the system - the car does not like it..... It still dumps Y amount of fuel into the cylinders.

Cheers

Sumo

the gtr was doing that for a while, just lacking power and stuttering under load. wasnt very violent, inet pressure stayed up, although the turbo's sounded like they were choking. it did it mostly when they would start to wind up. traced it down to a faulty O2 sensor...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • HFM BM57 has a "bad" knee point, IIRC. It's not the same thing as the later R chassis MC.
    • The ATTESSA is functionally identical to R34; there were a bunch of JDM models that continued ATTESSA including Fuga/Q70, Skyline/Q50, Cima etc as an option. All with Auto only and I think mostly for snow regions. AFAIK there were no AWD VR30DDTT sold in Australia - it is on my to do list to check regs for racing a LHD car in Targa/ATR/AASA/CAMS events because if I can get the auto to work it would be interesting to run a 4wd car The Ecuteck TCM tuning is the same model as their ECU tuning, they already have it for R35 and Dose's favourite, BMW. You buy "points" to allow your computer to be tuned, buy either a bluetooth (phone app) or bluetooth+USB+Key (phone and PC) dongle, and pay for a tune that will be locked to your tuner ( ). You can also access the tuning software yourself but 1. it is mega expensive and 2. these computers have a billion parameters that intersect, so how could you ever spend enough time on it to get a decent result.
    • Or, is it a case of what it is like owning an R series Skyline? NFI what the previous owner has done or fiddled with... Ha ha ha After reading through this thread, I went on a bit of a research about the Q50/Q60. Now I'm quite intrigued by them! Is the AWD in them more like a WRX where it's always AWD, or is it more like the ATTESSA in the GTRs? By the sound of this TCU tuning, this sounds like a case of someone has made some real software for it, and you just need the right piece of hardware, and then you license that specific vehicle/TCU. Or is this a case of the software will be really expensive so only a few tuners have it, and you still have to pay a license per vehicle?
    • By popular demand.. it was a coil. Got my hands on 1 new OEM coil, replaced with the one that made the less noise difference when I unplugged it while the car was running and started the car up. No stutter and the engine light was gone. I guess I’ll buy the other 5 they have lol
    • No, code 21 is very straightforward. It can only be the things described in that diagnostic flow. In fact it has no way of knowing that the spark plug resistance is out of spec.
×
×
  • Create New...