Am I running lean?

[madmike]

Try a 50/50 mix of Race gas or I hate to say it: Aviation fuel
You need some higher Octane

[buguy]

Yeah 10 psi is right on the edge of needing race gas. Try 8 psi and see how that works. Do you have a pic of the location of your AFR sensor location?

[advinnie]

I’m a aircraft inspector and using 110 aircraft fuel would cost me my job I was to borrow some
I’m fine at 8psi and that’s what I’ve dropped it to for now.
I’ve changed me exhaust system now but I had the sensor in two different places, first I had it in the small tail pipe 9” from the end and 2 meters ish after the turbo and then tried it 12” after the turbo and got the exact same readings
This was the reason I wanted/ thought about using meth injection to cool the charge and also cause meth is very good at not detonating

[Chip Birks]

I dont think Clonebug got much more out of his before he detonated. 10psi on pump gas is a pretty normal ceiling.

[Clonebug]

It all depended on the ambient air temps.
In the summer I would get detonation at around 10 lbs......in the cool spring and fall I could go a little higher.
We did tune the detonation out one summer by retarding the timing but I don't remember how much less timing we needed.
We only did it because when I was with Mario my WI turning on would kick his tuning computer offline.

I run as low as 18-20 degrees of timing even with WI at 20 lbs. Now with the intercooler and 73 degree boosted intake temps I am up to 25 degrees timing at 20.5 lbs and 4000 plus rpm.
At 160-175 kpa I see 29-26 maybe 27 degrees of timing. I haven't spent a lot of time tuning that area due to very seldom having the boost level that low. We did do a couple dyno pulls at 6 lbs. but never really adjusted the timing for better runs.....We went straight to the good stuff.....

It's an issue you have to learn to deal with........Draw through and Blow through deal with it and each engine is different.
Crank the retard in and get the detonation to stop......then work back up from there.

I still say you need to drive the thing and get some miles on it. leave the boost level alone and get to know your engine and how it runs and reacts at the boost level you are at.
Move that O2 sensor to within 6 inches of the turbo outlet and get at leat 12 to 18 inches of tubing on it to keep from sniffing the free air.

You can't tune if you don't have good, quality data.

[advinnie]

Cheers mate. Yes I’m also worried that if I’m getting detonation at 10 psi boost now with the air temperature at just 5 to 8 degrees C what boost level will I get detonation when the air temperatures increase to 25 degrees C ?

[Chip Birks]

Is the engine a stock 1600dp?

[advinnie]

It’s almost stock. It has a c/r of 7.4:1 or 7.5:1 I can’t remember of the top off my head. The only upgrades are forged pistons, engle 100 cam, steel pushrods external oil filter and cooler

[buguy]

I think stock they are 7.3:1 so I think that's pretty close.

[advinnie]

Hi all I’m still playing around with the exhaust system on mine and have a question. Now I know all about exhaust back pressure on a N/A engine but not to when it comes to a turbo engine. From what I can work out is the the turbo produces all the back pressure the engine needs but what happens if you was to restrict the tail pipe? I’m thinking it would increase the exhaust back pressure between the turbo and exhaust exit point and may be slow the response of the turbo?
I only ask cause when playing around I decided to put a stock Vw beetle tail pipe on and the volume decreased massively and it sounds pretty good but if cause this is restricting the exhaust a lot bench my question on back pressure. I was thinking about doing a twin tail pipe at the end. Anyway he’s a link to the video. The sound is not great doc to my iPhone mic playing up
https://m.youtube.com/watch?v=7kPAy6Ccj ... e=youtu.be

[buguy]

It will definitely affect the spool. Maybe you could run it both ways and watch your tach and boost gauge to see how much it changes. Of if it does. See if the decreased noise is worth it.

[advinnie]

Well today in the cold I fitted the stock tail pipes and had a drive. In a nutshell it doesn’t work. When off boost all was fine and it felt like the throttle response was better/engine felt it had more torque. But it definitely affected the over all performance, you could not hear the turbo spooling up, before you could hear the turbo spooling up at 2000rpm (in third) and boost building by 2200 rpm and reaching full 10 psi by 4000rpm but with the stock tail pipes on you lost the turbo spooling sound, boost didn’t start building till 2600rpm (in third) and at 4000rpm I could only at 6 psi boost and my gauge did at one point read 7 psi but only briefly. The biggest thing I noticed was the amount of heat coming of the down pipe and the turbo turbine case was unbelievably hot. So took it all back off and the turbo felt so much faster to kick in, boost increase again and the exhaust and turbo turbine housing stop pumping out unbelievably heat. The noise did sound good but the performance was not

[buguy]

Well at least you gave it a try.

[advinnie]

Yes I did. Can’t wait for this dam snow to sift so I can go play again

[buguy]

So weird. 88 degrees here today