BT/Revo, boost 9... what should I see peak?

[Spinnetti]

I finally put a boost gauge in... I expected the 20psi steady, but not the 25-30psi spikes I'm seeing... I also don't have the manual boost controller on.. is this normal? it runs mostly fine, but I seem to get spark blowout in 5th gear fully loaded (kind of a soft hesitation, but no pulled timing or anything, not temp dependant).. I've got the usual stuff from eurocode: evolution race works comp FMIC, Neuspeed TIP, Forge, ATP mani, APR exhaust, test pipe, 3.0 inlet snorkel, .025 plug gapped Denso iridiums (everything else missfires), SAI delete.

TIA

[A4 TSCHUSS]

boost 9 is 24-25psi it should hold right at that until about 6000 or so then taper off a hair

[Spinnetti]

so spikes to 30 or so (off the end of my gauge) are not unusual? What does the manual boost controller do? (I didn't fully understand what that does for me, so didn't put it in)..

[Grey D.]

are you running pump gas, or race gas and water/meth at that kind of pressure?

[A4 TSCHUSS]

never ran the car on boost 9 while on the N75 so not sure but I do know that on the N75 and boost set at like 7 it would spike to 24psi range and hold at around 20 so I would say it would be safe to say you would see a 30psi spike for a few hundred rpms when running boost 9 aka 25psi.

[Spinnetti]

Thanks for the info...

PS, I run 93 octane only. Interestingly, hot or cold temps, it runs pretty much the same (that is, very good except for foot to the floor, 5th gear above 100 or so when is subtly seems to be running a bit uneven - maybe clutch slip?).

[A4 TSCHUSS]

what timing are you running? 25psi is a bit much for pump unless you are running like timing 3. But you would be better off running timing 5 and 21psi

[F16HTON]

Boost 9 will peg the turbo everytime, basically the N75 is always closed on that setting. Requested boost is 2540mbar across the board.

[Spinnetti]

Is that too much boost? it runs fine, but sometimes does have a bit of hesitation. I'm running timing 6, and not having any trouble with missfires. Less timing feels wrong, but maybe I should bump the boost down a bit?

[dougyfresh]

Too much boost? Its all contingent up on your timing advance. If you are able to run that much boost with quite a bit of timing advance then you're making power. Most likely (and I think Greg and David will confirm with me) that you will not be able to run that high boost and still get quite a bit of timing advance. In other words, you'll make more power with a lower boost setting and more timing advance.

[Spinnetti]

Too much boost? Its all contingent up on your timing advance. If you are able to run that much boost with quite a bit of timing advance then you're making power. Most likely (and I think Greg and David will confirm with me) that you will not be able to run that high boost and still get quite a bit of timing advance. In other words, you'll make more power with a lower boost setting and more timing advance.

hmm... More timing that 6? i.e. should I run the timing way up and see what boost it will support? I thought timing 6 was pretty good? I logged it a while back, and didn't see any timing pull. In cool weather its enough to slip the (6 puck ceramic button) clutch at full load in 5th...

[Spinnetti]

Just a lil' update... I still need to log to confirm, but I pulled it down from boost 9 to 8, upped the timing from 6 to 7 and pulled back the fueling a bit (7 I think? - I forget). Anyway, I'm still seeing pretty high boost spikes (off the gauge), but it does run better than before and seems to have better midrange (I presume due to the timing)...

[A4 TSCHUSS]

The fueling setting with the sps3 doesnt do anything for us.

[diagnosticator]

Reduce the boost setting to achieve ~20-22 psig, and increase the timing until knock correction values of ~3 deg - =/< ~6 deg. are observed at full load.

When equivalent torque can be attained with less boost and more timing, that is prefered over less timing advance/more boost, because with less boost, there is lower intake air temps and the ECU can run ignition timing advance at the knock limit while controlling knock quickly, via timing retard for each cylinder, cycle to cycle. Boost control is a lot slower responding in comparison. Less peak boost allows more timing advance, will be more responsive driving, with less stress on the engine and turbo.

[Spinnetti]

Ah, thanks for the tips guys... I didn't realize the fueling didn't do anything on the SPS, and I can see how system hysteresis makes boost correction slow, especially since its a non-linear response. I'm already seeing better gas mileage by upping the timing - I'm back to stock economy pretty much (about 360-400 mi/tank). I'll pull boost back to 7 and and up the timing another notch and see what happens.

PS, what does the manual boost controller do for you? I have one, but didn't put it in (came with the turbo).

Thanks.

[A4 TSCHUSS]

mbc makes the turbo spool up a few hundred rpm earlier. You wont have linear power though. You will get up to around 10psi and then it will slam full boost. It makes a very noticable difference going to the mbc from the N75. The car seems way faster.

[Spinnetti]

Thanks for the MBC info...

So I went to timing 9 and boost 6. Runs the best ever! much better down low, and pulls hard all the way up in any gear now. Odd thing is, though it usually maxes around 22-23 psi on boost 6, it still goes to 25 psi sometimes, and I did notice it kinda oscillates at max boost sometimes. Finally, I think its "done" (except replacing my APR center resonator with a "sport" 2-1 collector - it keeps breaking).

[DEMI]

Thanks for the MBC info...

So I went to timing 9 and boost 6. Runs the best ever! much better down low, and pulls hard all the way up in any gear now. Odd thing is, though it usually maxes around 22-23 psi on boost 6, it still goes to 25 psi sometimes, and I did notice it kinda oscillates at max boost sometimes. Finally, I think its "done" (except replacing my APR center resonator with a "sport" 2-1 collector - it keeps breaking).

Have you logged your car with these settings? If yes, what timing correction #'s are you getting? If no, I would suggest you lower your timing and not play around with the settings unless you are logging the car. Remember that a lot of conditions effect your timing correction and this must be taken into account. Timing 9 on pump gas and no water/meth is way too much in my opinion.

[Spinnetti]

Have you logged your car with these settings? If yes, what timing correction #'s are you getting? If no, I would suggest you lower your timing and not play around with the settings unless you are logging the car. Remember that a lot of conditions effect your timing correction and this must be taken into account. Timing 9 on pump gas and no water/meth is way too much in my opinion.

Yeah, I do need to log it. Maybe tomorrow. I kept adjusting, and it kept running better and better. runs perfect now, never a miss, no spark blow out (running Iridiums) best mileage and low speed drivability since I started modding... I'll log it, but pretty confident based on how its running.