Like we discussed before best bet is to verify by reading plugs. Make a pull and shut it off, dont let it idle for awhile afterwards or its just going to muddy up the reading. If you dont see any signs then run it again and check.

 

Yeah thanks. I asked my tuner to do that. Btw can you tell me what the problem was you had with the fueling system. I know you had to pull out the basket again and if I remember right fuel pressure was initially to high. Im wondering if it has anything to do with the problem im having with the engine cutting off for a split second and the it comes back to life.

This doesn't happen very often but it concerns me.

I appreciate the fact that you care enough to still try to help me even though things didnt work out so great last time.

 

I just had to drill out the siphon jet more to get the base pressure down.

 

Oh ok. Is it possible for this to suck in any air causing a stall?

 

The siphon system works off of the return fuel flow so air wouldnt be "sucked" in because of that but if the fuel level is low enough you could run into a starvation issue. I always recommend people to keep it above 1/4 tank when boosting.

 

Ok, well if its not a fueling problem it must be electricle I guess witch makes me feel a little better because atleast I know im not running out of fuel under full throttle. Mabey I have a bad connection to the battery or something.

 

Nobody seems to think its real detonation but why would it go away after mixing race fuel if it isnt real detonation?

 

Oh, I guess I missed the part where it stopped knocking. I thought the "we even mixed in race gas" meant that it had the same outcome with the race gas.

Hmm, I'm not sure then. It still sounds like something strange is going on that isn't real knock. Maybe it's having a misfire that's causing some knock readings or something.

Did you answer whether or not you are using a detonation can or just looking at the oem sensor reading?

 

I dont know if he verified the detonation in any other way than just hearing it during the pull.
Been texting him but he hasnt gotten back to me yet.

He dose good work but is horrible with communication. Im sure he is frustrated with the issue as am I.

I think what u said about how it can detonate from running too rich might have some Merritt to it. That could also explain why my oil is getting dark if the fuel is getting past the rings.

Oil got dirty even during unboosted break in after about 300 miles.

Its really weird that it dosnt detonate on 5he dyno though. Even at 15lbs 560hp.
On the street its still detonating at 12lbs 540hp and we backed timming of 10 degrees.

Running 8 degrees of timming now.

 

so you sent your oil into blackstone for analysis after 300 miles? visual inspection doesnt mean anything. not sure why you keep thinking that. the only visual inspection you can take is looking for coolant or fuel.

 

I haven't sent a sample in yet. I wanted to finish the tune first and change the oil a few times first to make sure there aren't any contaminants left from the previous build.

Btw what is the correct procedure for collecting the sample?

 

This block is on its third rebuild. The oil from the previuos two builds didnt get dirty so visual inspection tells me that someting is different.

 

I think they have sample tubes they will send you. Just drain the oil and fill them up from the stream as it comes out of the engine and send it back. If you collect it yourself make sure it's from a completely clean container and not a dirty oil drain pan.

If it's actually detonating loud enough to hear in a street pull then that is serious knock and your plugs would show it. I had an issue with one dome on my head that caused a hot spot then some detonation only on 1 cylinder. It wasn't able to be heard and it didn't even cause my knock control to adjust anything but I saw it one just that 1 plug. I fixed the issue and everything is good.

Audible knock would cause some noticeable damage. The fact that it happens on the street when the whole car is moving and not when the car is tied down in place is what is making me think something else is causing the noise.

 

Intersting. Thanks for the help. But that still doesn't explain why it goes away when I add race gas.

 

I just got back in town and I am going to meet with my tuner tomorrow (today actually) I hope he figured it out. Ill let you know what I find out.

 

So on the street with race gas it doesn't detonate?

I guess I'm still confused so I'll run down what I have come to understand:
Dyno car: no detonation
Street drive car: detonation
Street drive car+ race gas: detonation
street drive car on low timing and reduced boost: detonation


I'm still thinking 2 things need to happen no matter what. Oil analysis and checking the plugs to pinpoint if and where the detonation is. I also think at that boost level 10* (or 8* now) timing is way too little.

 

It sounds like it goes away with race gas/higher octane fuel mix, which rules out phantom knock/mechanical noise.

My guess would be on some kind of hotspot.

OP you're definitely going to have to pull those plugs. If you had det on one cylinder and lean conditions on another there was some kind of problem. Is this on the same heads by any chance? Any parts being re-used?

Also if your tuner is using a dyno jet, he isn't loading the car the same way as on the street. Increasing load on the crank definitely changes knock thresholds.

 

Update... car now has over 4000 miles on this build. Im in boost all the time. I drive it like I stole it.couldnt figuer out why it very infrequently cuts out on hard right hand turns but I had my tuner go through the fueling system and he found nothing that would be causing this problem.

I guess the prob must be electricle wich is good because it means im not running out of fuel.
Also this has only happend once in the last 3500 miles or so so I guess I can live with it.

Im making 530 to 560hp (depending on weather conditions) at 13lbs of boost. On 91oct.
To prevent detonation on the street I have been adding a few gallons of 110oct per tank.

Its a little expensive but its an effective treatment to the unfound cure.

Im going to put in a meth kit to get more hp and see if I can run straight 91 on the street without detonating. If I can do that it will pay for the kit in a short amount of time whith the $ I save from buying race fuel plus I will get alot more power.

Hopefully I will be able to hit low to mid 600's on 91 wi5hout detonation on the street.

I want to thank everyone who helped or commented along the way (good or bad) as it has helped me alot. Im still not even close to an expert but I have gained essential basic knowledge that will help me maintain, diagnose, and repair my ride.

 

Street drive car plus add race fuel= no detonation.

 

I have had the MTM setup for almost 2years now , we noted early on that the MTM recommended fuel can mods (drilling three holes in the bottom of the can was a really poor idea. On mine and others it resulted in fuel starvation on low tank levels and hard turns. So if you have followed those original MTM instructions ,that is the likely root of your starvation issue..