ok. ive noticed on a hard downshift with a normal fuel setup in our cars (normal being larger injectors and a SFMU), you get slight detonation when downshifting right into the powerband. i dont know if its lag from the sfmu to dumping fuel into the cylinders or what, but it always happens. im sure you turbo guys know what im talking about.

i was wondering if the megasquirt can combat or fix this, and how it handles that, just out of curiosity.

Aren't the 8 injector guys getting that even? Seems to be a plague. Maybe it's something you can tune out with a slight timing adjustment. :shrug If so than I'd say that megasquirt could deal with it.

first of all. i dont have those issues with the portfueler.

second.. why would you want to do hard downshifts? do you like beating up your car for no reason?

Originally posted by siueclipse
first of all. i dont have those issues with the portfueler. second.. why would you want to do hard downshifts? do you like beating up your car for no reason?

Really? Have a knock meter? Do you like accelerating in 5th gear at 2k rpms?

LOL, it is called downshifting and people with large size turbos that spool slower use it to aquire some decent boost instead of waiting for ages. How is he beating his car up for doing that?

Maybe the 400hp goal was for a LONG 5th gear pull....no wonder it's not there yet.

JUST KIDDING :)

Originally posted by soulcontroller
ok. ive noticed on a hard downshift with a normal fuel setup in our cars (normal being larger injectors and a SFMU), you get slight detonation when downshifting right into the powerband.

I've NEVER seen hard evidence of this. Jason and Matt both got signs of knock using the MSD knoxk box, but I really think that thing is inaccurate.

Originally posted by soulcontroller
i was wondering if the megasquirt can combat or fix this, and how it handles that, just out of curiosity.

Even if it is knock that some guys are experiencing, it would be completely controllable using the MS, since both fuel and spark maps are set by the tuner.

Yeah, I do get that slight amount of det too, both audible, and visual from the MSD knockalert. BTW, I use the knock sensor that came with the MSD..I've only really noticed this on a 5th to 4th downshift, when going WOT, and only happens around 15+ psi boost, and ONLY for 1 second. During the 5th to 4th downshift, the RPM band is smack dab in the middle of peak torque, and also, which i think is the main culprit- we are getting just a few too many degrees of spark advance. Combine the spark advance, boost level, and peak torque band during the downshift, detonation happens. I know for a fact it is det, because I can put in some 100 unleaded in the tank, and the rattle is completely gone. Unless your windows are up, and have a keen ear, you may never, ever hear it driving..

This is why I think the MSnS setup will be perfect for. We know have total control of timing under boost. I will be installing this setup hopefully over the winter, and I am going to see how much power the S16G can make on pump 93 octane..I believe once we reach around 15 psi, we are maxing out our stock ignition advance with pump gas and 8.8:1 compression. I'll probably back off the timing 3-4 degrees during peak torque at 15+ psi, then put a few back once out of peak torque up to redline..I'm almost positive that will cure the rattle.

No detonation here... no rattle.

Does that answer your question?

When you can control everything... well, you can control everything... :)

Originally posted by MrSlick
No detonation here... no rattle. Does that answer your question? When you can control everything... well, you can control everything... :)

If I had the Megasquirt, then I could control everything, that is of course, having it. The mere thought of it won't help, right Mr. Slick? :P Lee, check your PMs.

Anyone have logs with this??

It would be nice to be able to log the AF ratio when the shift happens...along with the RPM/TPS logs and knock count

Im going on a limb here but i say this might be because of the fuel pressure needed lets say cruising in 4th (you are auto right?) gear at 3k rpm, then go WOT get a downshift, turbo spools like a mother ..leaving the SFMU having to up the pressure to 5k rpm/wot conditions in a hurry..(correct me if im wrong in the assumption of this..since the pressure differential on a SFMU system is huge between partial throtle at low rpm vs. full throtle in the peak of tq curve)

I beleive any standalone with a 1:1 regulator should keep the pressures in a closer range (therefore also fuel flow), therefore react quicker to provide enough fuel? right wrong?? imput

Originally posted by BlueMoonEclipse
Anyone have logs with this?? It would be nice to be able to log the AF ratio when the shift happens...along with the RPM/TPS logs and knock count Im going on a limb here but i say this might be because of the fuel pressure needed lets say cruising in 4th (you are auto right?) gear at 3k rpm, then go WOT get a downshift, turbo spools like a mother ..leaving the SFMU having to up the pressure to 5k rpm/wot conditions in a hurry..(correct me if im wrong in the assumption of this..since the pressure differential on a SFMU system is huge between partial throtle at low rpm vs. full throtle in the peak of tq curve) I beleive any standalone with a 1:1 regulator should keep the pressures in a closer range (therefore also fuel flow), therefore react quicker to provide enough fuel? right wrong?? imput

Well I believe both matt and jason are 5 speed guy's so that kicks the auto thing out. They were also both using the 8 injector setup (w/ 1:1 reg)while recording these results. I believe what they were seeing could be a combo of so many factors. I do not get this at all with my star kit. So I believe the turbo, and the timing to be the main culprits as the turbo is what makes the peak torque and the peak boost... Does that make sence???

Originally posted by Kirby

Originally posted by BlueMoonEclipse Anyone have logs with this?? It would be nice to be able to log the AF ratio when the shift happens...along with the RPM/TPS logs and knock count Im going on a limb here but i say this might be because of the fuel pressure needed lets say cruising in 4th (you are auto right?) gear at 3k rpm, then go WOT get a downshift, turbo spools like a mother ..leaving the SFMU having to up the pressure to 5k rpm/wot conditions in a hurry..(correct me if im wrong in the assumption of this..since the pressure differential on a SFMU system is huge between partial throtle at low rpm vs. full throtle in the peak of tq curve) I beleive any standalone with a 1:1 regulator should keep the pressures in a closer range (therefore also fuel flow), therefore react quicker to provide enough fuel? right wrong?? imput

Well I believe both matt and jason are 5 speed guy's so that kicks the auto thing out. They were also both using the 8 injector setup (w/ 1:1 reg)while recording these results. I believe what they were seeing could be a combo of so many factors. I do not get this at all with my star kit. So I believe the turbo, and the timing to be the main culprits as the turbo is what makes the peak torque and the peak boost... Does that make sence???

You know, I've thought about that quite a bit, as it seems no one with a larger/more efficient turbo complains of this issue. I've tried every dam thing I could think of to get rid of it..still no luck. With the 034 controller, I've dumped in shit loads of fuel at 15 psi and right before and during peak torque, and it helped, but it was still there. I'm talking about around a 10- 10.5:1 AFR too! Richening up the A/F ratio to combat detonation is just not the way to making good HP and torque. I run pretty rich too, around 11.0:1 at 15 psi, and it should not be detonating at that A/F. It's timing related, at least for 93 octane fuel.

If you stop and think about it, the ECU is programmed to run its timing advance for a NA motor, 87 octane. Our stock advance isn't really aggressive, but it's about right on for a factory setup, running 9.6:1 compression. So now, we drop the compression ratio to around 8.8:1, run 92-93 octane fuel, which gives us quite a bit of room to run boost on stock timing advance. The pentroof combustion chamber design of our head, really helps the det issue, but hell, getting 15 psi boost without pulling ANY timing is pretty damn good I think. On boosted motors, the hihger the cylinder pressure, the less timing advance you need to light it off(for a given fuel octane). Even by pulling out some timing doesnt make for the best power potential, but aside from running higher octane fuel(and lower boost pressure),it's the only viable option.

You want to make serious power? High boost, highest octane fuel available, and as much timing advance as you can get without knock...
Fuel octane is pretty much our constant, and timing and boost pressure are our variables we have to work with. A/F ratio should stay fairly consistant as boost pressure raises, maybe a slight richening of the mix as boost gets highger though. Seems like the boosted 420A likes around 11.3:1 to around 11.8:1 or so in higher boost for good power.

no problems here, downshifting to 3rd at 40mph running 20psi.

Originally posted by grain
no problems here, downshifting to 3rd at 40mph running 20psi.

What are you using to detect/log knock? I sure hope you don't say "my ears".

Aha there goes that theory :)

Originally posted by grain
no problems here, downshifting to 3rd at 40mph running 20psi.

Downshifting to 3rd at 40? That isn't much of a downshift is it? I downshift to second at about 38mph and floor it...putting me at about 4,500rpms and rising but pulling hard as hell. Downshifting to 3rd would be more like at highway speed...downshifting from 4th gear at 60mph into 3rd...

it been awhile since i did any kind of pulls. i burn out anything close to 2nd gear. hell. at 80mph ill downshift into 3rd and ill still burn my tires at 20psi

maybe we can meet up since im in illinois till the 14th

Once I drop my new motor in (2 months roughly) I'm wondering how my traction will be at 20psi...

I know they spin like hell...but I'm rolling 19's with BFGoodrich Scorcher tires.....half the tire is basically a slick - it is comletely smooth. At 8psi I even noticed a HUGE traction gain from switch from my old rims and tires.

With my 18" old tires I could go full throttle 8psi thorugh first....shift into second and the tires would break loose slightly then hook up. After switching, I can't even burn these ones out hardly at all and shifting to second they just grab hard....So maybe it won't be THAT bad.

Plus I plan on running some sort of dual stage boost controller to limit 1st gear to 10psi....then up to 20psi after getting into second.

Originally posted by grain
it been awhile since i did any kind of pulls. i burn out anything close to 2nd gear. hell. at 80mph ill downshift into 3rd and ill still burn my tires at 20psi maybe we can meet up since im in illinois till the 14th

Are you using a LSD?

For the people that run MS, do you guys log your info and sensor feedback or does MS support closed loop feedback from the O2?

If so, can you guys post some logs of a tuned MS system to see how good it runs?

yes, i have the quaife lsd. i have 16inch rims with falkin azenis. 20psi 25g turbo, bout 340+- to the wheels will break loose in top of 3rd easy.

So, I'm guessing the MS doesn't use closed loop feedback?

Originally posted by SilverBullet20g
So, I'm guessing the MS doesn't use closed loop feedback?

Actualy you can make it run closed loop ....just need a good WB02

I remember reading a string over at an EVO board where timign was measured. Apparently, after each shift, the timing would be pulled back a few degrees to apparently prevent this very thing. Of course, that was on a stock EVO computer. I've read about this same issue though on a subbie board, so this issue is quite real.

The MSD knock box may not be the most accurate device in the world, but it's consistency during shifts and high boost runs are unmistakeable. That certainly lends itself to some amount of credibility.

Hrrrmm, I've never had this problem. Perhaps I did and didn't hear it, I really need to pickup a knock sensor. Regardless I'll be finishing the install of my MS today. :)

dirk congrats and good luck on the install. by the way? what turbo setup are u runnin? thanks ben