PyroVTEC

I can't get beyond 7psi of boost w/out detonation!

Here's the kicker though... I'm running 550cc injectors on the D16Y8, with an AEM EMS driving them. Static compression are through 9:1 SRP pistons on California 91 octane pisswater. Plugs are gapped at 0.030," thru a Crane ignition system. Fuel pump is a 255lph Walbro in-tank, stock fuel pressure.

The knock sensor (KS, in FSM-speak ) starts to get a little active around 7psi (registering 1.5-1.6 volts or so). I don't know if the KS is picking up piston slap or not, but one would have figured a standalone would be able to take care of detonation. We've tried dumping in 10% more fuel and pulling out 10 degrees of timing--still the same 1.5-1.6 volts from the KS.

Although 193whp/176tq is pretty good for a SOHC Y8 @ 7psi (thanks Darren!), I would have thought I'd get at least 11psi of boost from my setup. After all, isn't VTC_Civic boosting 12psi w/out problem??? And he's getting somewhere around 210whp!

Any ideas/suggestions on what's up?

PyroVTEC

Anyone?

Spade

You should talk to VTC. He was pushing 9.5 PSI on his greddy kit.

falcongsr

if you're pulling timing and adding fuel and seeing the same knock raw signature, then you're likely not pinging. i think i see 1.5v on the ems with a stock motor sometimes at high rpm.

what is your exhaust setup, that really chokes off the mistu turbos with the internal wastegate. i was struggling to see 4-5psi with stock exaust...open dp i am spiking to 9 before i even hit 4000rpm

Overblown-Teg

I agree with falcon.. can you disconnect the wastegate to see if it knocks with zero or very low boost. sounds like engine "noise" to me

PyroVTEC

It's REALLY weird... At 0 vac/boost, the knock sensor is silent. At WOT 5psi, the knock sensor is silent. It's only at WOT 7psi around 4600-4900 indicated RPM will you see the knock sensor come alive at the 1.6v or so. Also, I hear the heart-stopping marbles-in-a-can sound around there too--sure sounds of detonation, no? It's awfully strange and disheartening!

falcongsr

if your exhaust is restrictive, you WILL get detonation.

remember that however much boost youre making, theres more backpressure in the exhaust manifold..usually about 1.2 - 1.8 times the boost level. for every psi of backpressure AFTER the turbo, add that to the amount of pressure in the exhaust manifold.

if you're boosting say 7psi, then you have 9psi in the exhaust manifold (being very conservative)...

then you have a restrictive exhaust that causes 3psi backpressure, guess what, you have 12psi in the exhaust manifold, and sometimes its just gonna be easier to go back into the cylinder then try to squeeze out the turbo into the exhaust.

and since pressure is directly proportional to heat, you end up with a bunch of VERY hot gases hanging around your engine.

and your motor goes ping pang walla walla bing bang.

someone check my logic here. and pyro i dont know if this is your problem or not but you might want to consider it.

PyroVTEC

Heya Falcon... thanks for the reply... How's your EMS doin?

About the exhaust question... running 2.5" piping from the downpipe back. Yes, I do realize that more people run 3" piping, but from what I understand, a 2.5" setup will be fine to at least 300hp or so. I formerly did have a cat that crumbled and just jammed the entire exhaust, and I couldn't boost any further than 1.5psi due to the exhaust restriction and all. Since then, the aforementioned problem has been attended and amended.

Dramier

Are you intercooled? This sounds alot like the air is heating up too much at 7PSI. I vented to atmosphere a while back when it was still hot temperatures outside and got ping at around 17PSI. (don't ask).. well, yesterday I boo-boo'd and twisted the MBC too far and went to 20PSI on accident with no ping this time. (No fears, I turned it back down to 12PSI)

I'd be willing to put money on it being the intake air being too hot. Almost any boosted application you have to intercool to stave off detonation after 7PSI in smaller liter engines. In Z's you can go up to 10-14PSI, but after 12PSI you generally have to intercool to avoid detonation caused by temperatures being too high. If you can, run an ambient air tempature sensor into your intake and check it out. Good luck, and hope this helps.

PyroVTEC

I have the Greddy Type 24 intercooler. According to Greddy, it's rated to 550hp, which is ummmmm....... a liiiiiiitle more than I expect out of my little SOHC.

lazerus

intercooling becomes increasingly important as compression ratio, and boost rise.

my friend on a 2.3L ford runs 14 psi non intercooled no problems. on 91 octane. but the compression ratio is like 7.xx:1 and we're at 5,000 ft. so that makes a difference.

SJP0tato

Do you know what the timing retard per psi of boost is set at? I've noticed with mine (running zdyne) around .5 degrees per psi would cause pre-ignition, now running at .7 retard per psi and I'm ping-free.

Just curious what you're set at,

Ryan P.

bretx0r

did you buy colder plugs btw?

PyroVTEC

Ooh.... this is a very good suggestion... I can't believe I didn't think of this earlier! I will have to check, but to my understanding, I think it's 0! Maybe that's what's causing the problem... Only confusing thing is that the EMS operates in kiloPascals (kPa), and I haven't the formula for converting to English units... (hint, hint )

BTW, plugs are new; BCPR7ES plugs gapped to 0.029."

JAMinCiViC

iTrader: (3)

Here's a site for converting #'s

http://www.convert-me.com/en/convert/pressure