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View Full Version : Flat spot when EBC working.



Beastlee
04-02-2010, 06:13 PM
One of the tings I was suffering before the EBC stopped working was a harsh flat spot, a quite sudden jolt part way in the band, at around 3500RPM. When the EBC was dead this wasn't the case. I assume therefore this is a boost issue and related to my EBC settings.
I am running the E-01 at Set 38/Gain 35/Start 9.0 so I think it could be that the start pressure is 2psi over the standard boost pressure. Other than this particular issue the car seems to run fine and doesn't overboost or fuel cut right now, i even holds 12psi quite happily.
I was thinking of dropping the Start a little but not sure how that will affect the overall boost. Perhaps I have too much set and not enough gain, or vice versa?

Any of the tuning afficionados able to suggest the best way to fix it?

Turbo_Steve
04-02-2010, 08:08 PM
OR it's detecting some knock and pulling a load of timing. Given that it's not fuel cut (you know what that feels like) and it's not spark snuff (as I believe you've already dealt with that with colder plugs) I would suggest that the ECU is perhaps reacting to some detonation and winding the timing back in hard.

That's certainly congruent with the EvoScan logs you sent me?

Beastlee
04-02-2010, 09:06 PM
Steve, I haven't yet changed the plugs but you have reminded me I need to! Having taken the car out tonight it really felt good. I did notice that it seemed happier in auto than it did in tip so I suspect that part of the problem may be the ATF flush that is a week overdue!
I'm going to get another log done as I think things have changed a lot since the alst scan you reviewed. It certainly feels different and the TRE pump has removed any sign of fuel cut.

Beastlee
06-02-2010, 08:48 PM
Have done the ATF and it feels smoother but hasn't fixed the odd power curve. Ordering the NGKs ASAP.

Eurospec
06-02-2010, 11:58 PM
When you generate more boost, you generate a steeper torque ramp. The torque converter can have trouble dealing with that- so yet get this kind of lag where the tc is catching up.

It feels like the car sets off and goes like stink, then kinda hangs at a certain rpm, before powering through it.

does that sound like what you've got?

Cheers,

Ben.

Beastlee
07-02-2010, 12:31 PM
Ben, it's more like the power is cut for a second and it's not always present. I'll get the profec to do some logging and see if it's obvious on there.

Would the torque converter also cause my odd surge when accelerating in 5th? ie. approx 80mph accelerate hard but don't shift down, let off the accelrator and the car almost surges/lurches before it settles back to cruising? Doesn't take more than a second of throttle to trigger this.

Turbo_Steve
07-02-2010, 01:08 PM
That sounds more like a dumpvalve related issue, Lee.

And thanks for the Torque Converter comment Ben.....mine does that!

Beastlee
07-02-2010, 02:18 PM
I have literally just found my stock BOV in the garage and will refit it, not that I think it will handle the upped boost properly. The one on now was an alloy model I got from WODJNO a long time ago and is very loud considering it's a recirc model.
What would be wrong for the BOV to cause the issue?

Will do a search for BOVs on here as I'd like to find one of those recirc and VTA models so I get the noise :)

Turbo_Steve
07-02-2010, 02:51 PM
The problem with weak dumpvalves can be, especially with recircs, that the negative pressure on one side, and the positive on the other can be enough to cause it to partially open at certain pressures, creating a flat spot. This generally only happens at partial throttle, or if you lift off during hard acceleration, and is due to the pressure differential at the inlet manifold and the throttle plate not being large enough. If you search for "Hysterisis" you'll find a Pitslayer thread with a long-winded explanation.

The other issue with dumpvalves is that the release air from the "closed system" metered by the MAF. So if you lift off and re-apply the throttle with a VTA fitted, the MAF meters extra air into the system. Unfortunately, the ECU doesn't know that this air is replacing what has been lost by the VTA, so it thinks there is now more air in the system than there is. It doesn't want to run lean so it increases the fuelling dramatically as you put your foot back down, resulting in a "Boggy" feeling of hesitance.

Beastlee
07-02-2010, 03:00 PM
I'm intending on going to hybrid at the most not a pure VTA. Been looking through the threads as I remember there being a highly rated one. Can't find it though!

Turbo_Steve
07-02-2010, 03:55 PM
I've not tried one, but I am utterly unconvinced by Hybrids: you're opening both your inlet tract and throttle tract to the atmosphere. If opening one side is bad, opening both is far from likely to be better.

That said, the chaps on here seem to get good results with them. Mind you, nobody on here has posted about the throttle issues at higher boost, and everyone must have suffered them at some point.

It's funny how easy it is to completely ruin your car without noticing. :( Especially with regards to smoothness.

Beastlee
07-02-2010, 04:05 PM
Mine is mostly smooth but just these these niggles then I'll be happy.

Turbo_Steve
07-02-2010, 04:18 PM
Sorry Lee, yes, it wasn't meant as a dig at you, or indeed anyone in particular!
Apologies if it came across that way.

Beastlee
07-02-2010, 04:24 PM
Steve, wasn't taking it that way, you've been far too helpful for me to think you'd make a dig LOL

I realise how much a small change can make to the car and you're right. Mine isnt as smooth now simply because I've played with it. it would help if I knew what I was doing a little more LOL
I imaginr the fact I'm still not using the e-mange isn't helping. Really must find a place ot set it up properly for me.

Forgot to add that I've ordered 6 x BKR7EIX to be fitted as soon as I get another dayto work on the car LOL Poor thing must be fed up of having my hands all over it's internals LOL

Roberto
07-02-2010, 06:22 PM
I have one of the GFB Hybrids fitted for the last 4 odd years, bought from another member (BDA) and apart from needing to give it a good clean once in a while (note to self to do that job again), it works perfectly with no issues holding boost.

But I don't have a TC to worry about.

raph
07-02-2010, 08:02 PM
Your emanage is in but you havent touched it yet? ive remapped cars with different piggy backs before..albeit some are easier- i can have a look once your wideband is in if you like.(assuming you have the access cable etc /cd)


Roberto..your vta hybrid doesnt stall the engine after say boosting in 4th,then pressing the clutch rolling up to a red light..no stumbling?

Beastlee
07-02-2010, 09:31 PM
Raph, it's all installed. Everything is linked up to the laptop, I can log all of the relevant info now ready for tuning.
If we meet up I'd love it if you could see what you think and can do with it.

Roberto
07-02-2010, 10:22 PM
Roberto..your vta hybrid doesnt stall the engine after say boosting in 4th,then pressing the clutch rolling up to a red light..no stumbling?

Nope, but then again, I wouldn't stop at the lights like that anyway.

Beastlee
08-02-2010, 06:11 PM
Clearly all the time away from my car has left my brain a little addled. The issue isn't that I have a flat spot it's that if I let off the accelerator whilst boosting it acts like a slightly less harsh bout of fuel cut. It's very harsh when you lift off at approx 2500rpm in 1st or 2nd following a liberal application of the loud pedal.

I finally got to drive the car with a little anger as I was logging some data earlier. Goddam it felt quick off the mark, it's just a shame I have no way of seeing the speed tied into the log for now. I must reconnect the speed sensor wire with a switch.

raph
08-02-2010, 06:23 PM
and thats with the vta fitted? sounds like overfueling/bogging.. do a log and show me

Beastlee
08-02-2010, 06:28 PM
Raph, no that's just an EVO recirc fitted. I haven't gone to a VTA although it is very loud for a recirc. I also noticed I whistle whilst keeping it floored, I thik its the tubs and the downpipes but could be air bypassing the valve. The boost line oscillates slightly which I suppose could indicate the loss of pressure being compensated for by the EBC.

Beastlee
10-02-2010, 09:41 PM
Tried to refit the stock bov but unfortunately the vacuum connection snapped off so the alloy one is cleaned and refitted. Almost spotless anyway, no sign of oil leaks.

Beastlee
14-02-2010, 06:00 PM
Well did the plugs today, will update my project thread with the nitty gritty.
The big surprise was to find that the car had Denso Iriduim 20s in there already. They appeared to al lbe gapped to 0.8mm and were looking fine. Oil seal on the back left is leaking but other than that I found nothing to worry about. anyway the NGK iridiums are in now and the car does sound and feel much better than before. Time will tell.