Fuel questions: detonation?

[fuforums]

I have a 2.5 intercooled with the mitsu turbo. Only mods are grainger valve and the intercooler. I just got this beast running from storage and it's awesome. Thing is, seems like there is a tinny sounding noise when I get on it pretty hard but not when just revving in neutral. My A/F meter shows green lites at WOT not even in the orange middle section but I'm wondering if that is detonation I hear or maybe an exhaust leak? My pipes are in bad shape and I haven't been under there but I don't want to blow anything up before I get a new exhaust system. With a stock system like this and only running 12psi surge leveling out to 10psi I shouldn't be having a fuel problem, right?

Joe
91 Shadow Turbo Intercooled 2.5

[WVRampage]

What do the plugs look like,but you shouldnt be at the limit yet.

[turbovanman²]

What octane gas? 10-12 psi is about max on 87 pump gas. Whats your base timing set at? you could also have sh*t gas still in the tank. What your hearing is detonation, you can still have enough fuel but you can still get it.

[bn880]

That does sound like detonation from the description. The only way I could see that happening is as mentioned, ---- gas, low octane OR, terrible heat soak and much advanced timing. (not likely)

[shadowdude]

What octane gas? 10-12 psi is about max on 87 pump gas. Whats your base timing set at? you could also have sh*t gas still in the tank. What your hearing is detonation, you can still have enough fuel but you can still get it.ok so whats your opinion on the max boost for our crappy 91 octane here ??? with the big intercooler and all the good stuff of course .

[fuforums]

I have a bad head gasket so it could be because of that. Going to change it this week when it comes in.

[turbovanman²]

ok so whats your opinion on the max boost for our crappy 91 octane here ??? with the big intercooler and all the good stuff of course .

Probably 14 ish, :(

But Paul has been known to tune for bad gas, I think 8valves layed down over 300 whp and 300 ft/lbs on pump gas.

[shadowdude]

I really really really really would like to make 275 whp on 91 octane gas.Were or who ( Paul? )is the best to get a SBEC calibrated for this ?? I would obviously give them complete details on what i have for a set up.it has to be possible ,man i want it so bad i can taste it.

[Una]

I have a bad head gasket so it could be because of that. Going to change it this week when it comes in.
Or it could be the other way around.. Detonation usually causes blown head gaskets..

[turbovanman²]

I really really really really would like to make 275 whp on 91 octane gas.Were or who ( Paul? )is the best to get a SBEC calibrated for this ?? I would obviously give them complete details on what i have for a set up.it has to be possible ,man i want it so bad i can taste it.

Paul is the cal tuner for www.turbosunleashed.com Contact Chris and Paul is hard to get ahold of these days.

[shadowdude]

Oh BTW one more question,if I have a walbro 255lph pump,52pph injectors ,a 4 to 1 rising rate regulator and my static fuel pressure is 30psi and i am using 91octane and timing is @12* HOW CAN I STILL BE RUNNING LEAN at 18psi?? my EGT gauge goes right up to and past if i let it 1500 degrees in less than 30 seconds under WOT.I am getting really frustrated with this car.:banghead:

[bn880]

It can if a regulator is not working properly. get a fuel pressure gauge installed and look at it when you boost.

[shadowdude]

All right ,i will do that today and post back A.S.A.P ,thanks .

[shadowdude]

Well ,I put the gauge on and went out and tried it and of course ,even though i am seeing 50psi at full boost 18 psi ,it still wants to climb right off the scale on the EGT.this is so not right!! I have everything the way it is supposed to be but for some stupid ,one in a billion reason it just wants to keep going lean.i am sooo close to just getting rid of this car ,i have never had such a hard time with a car as i have with this one.Three years of money speading and wrenching and i still cant win !!:censored:

[shadowdude]

ok so ,after calming down and using my head ,i now see that i figured wrong and 18psi of boost on my set up for fuel should see 72 psi of fuel pressure ,which i am not ,so i have a "stupid" question,can you hook up a RRR backwards? besides that what else ?? the adjustable is new,any more than 30psi static and it will be friggen hard to start. sigh why didn,t i take up knitting instead.

[contraption22]

2.5's with swirl heads are extremely sensitive to spark knock. Take a degree or 2 out of your total advance.

[shadowdude]

Yup ,i agree ,and I will be timing to 10*.Stock calls for12* of course.What i dont get still is why am i only seeing 50psi @WOT ??? I need 70psi ,well ...72psi to be exact.

[Una]

Weak fuel pump.. Runnin a Walbro 255 yet?

[shadowdude]

Yup ,running the walbro 255lph ,along with what I listed up above .This is why i am stumped as to why i am running low pressure at WOT.It just doesn,t make sense .:confused: who ever figures this one out it a master TD tech ,cause i dont get it thats for sure.

[bn880]

Well it's pretty obvious the RRR isn't working properly for you. I mean, you could first do a pump check by closing off the retun line for a second and checking if you get near 100psi of fuel pressure. It sounds like you are running only on your primary regulator @30psi + 18psi fuel pressure (due to boost gain).

YES it's possible to hook up a RRR backwards. :D (you have a primary AFPR and then a RRR right? Or is it an all in one with static adjust and a 4:1 gain?)

Basically if you have only one regulator and it is the RRR, it's not working as advertized, it's working as 1:1 gain.

[shadowdude]

Yup i have a AFPR on the fuel rail to adjust down to 30psi ,to compensate for the 52pph @idle ,then i put the RRR in between the return line. I am going to double check the pump with that test you siad .I guess i will go and try switching the two fuel hoses on the RRR.Thats what i was wondering when i was asking about the backwards hook up.The Vortech RRR 4 to 1 i have doesn,t have any markings to show whats in and out on the barbs.I will keep posting of what i find out.I am still scratching my head on this and i appreciate your help cause it is hard to think clearly some times with this car ,it has been one stubborn build with it.It has a curse on i,m sure.:rolleyes:

[shadowdude]

Ok i just went out side and tried closing off,(pinching) the return line.got up 70psi at idle and when you rev it up it goes up to 90 psi right o way .so to me,anyways, that shows the pump is working. what next ?

[bn880]

Here is all i could find:

3 ports on FMU the one on the front is the vacuum port, the one on the side is fuel IN and the one in the middle is fuel OUT.

Make sure that is all correct, then check the vacuum to it is actually coming in and is not blead off somewhere. If that is all good, the vortech is bad.

[shadowdude]

Ok great ,I will swap the two around.I will also check the vacuam to it.Thanks alot :thumb: i appreciate you looking that up for me ,i couldn,t find that info anywere.I will let you know what the results are.

[shadowdude]

well ,I did switch the hoses on the RRR and it solved my low fuel pressure,so thats one done,but.....yes as i siad cursed car,there is another problem.now the pressure shoots up with the boost so at half throttle it will fall flat on its face ,you would swear that it was the rev limiter ,but any ways if you frig with throttle and stuff then catch it just right and go WOT it will haul,EGTs are only going to around 1250 @WOT right up to 200kmph.So how am i going to get rid of that HUGE flat spot in the thorttle ?? some days :rolleyes:

[bn880]

I think that's just your gain 4:1 on the Vortech, if you compare the boost to the pressure it will probably prove that. It's a rather unfortunate reality if you have a non adjustable secondary regulator. You could try putting in a restrictor orifice and some bleed valve right before the regulator, to drop the pressure on the Vortech and to slow its gain... rather complicated.

I myself am currently fighting a Cartech 20007 secondary adjustable gain regulator to actually adjust properly, so really you aren't far behind me now in tuning. :lol:

I'd like to hear other people's experience on how much gain they run on their secondary with 52lb injectors.

EDIT: To my knowledge a nice gain is 2.5:1 to 3:1 (it all depends on your mods, like porting, exhaust size, IC size etc)

[shadowdude]

Yea ,the final stages of tuning can be testing.I had info that the 4 to 1 was the closest with the 52,s but i am having a instant spike in boost along with fuel pressure .I am thinking if i can control or slow the boost response then in turn the pressure spike in fuel from the RRR would respond the same ,The boost controls the speed of rate in the RRR right,so if one is getting a fast spike in boost it would spike the fuel pressure .The graiger i have is allowing it to get into boost even at half throttle so see were i am going with this . I think it would work .wondering how the adjustable RRR would work to ,but you say it is hard for you to tune also?

[bn880]

Yes right now the adjustable RRR is giving me some headaches, but it seems that by adjusting the needle valve on it I do get to slow down or speed up the rise a bit (going to rebuild the ARRR this weekend). You can try installing a restrictor orifice and then a needle valve before the 4:1, you should be able to to control it's response that way, but just don't lean it out too much. :) Otherwise it's time to buy a fully adjustable reg.

Edit: If you install a needle/bleed valve, put a one way check valve on the output so that you don't suck dirty air through it.

[shadowdude]

guess i am going to have to buy the fully adjustable one,I tried the bleed in the vacum line going to the RRR practicaly had it bleed wide open all the way but even at half throttle it is still is dumping fuel way to much.when i watch the fuel pressure gauge the needle is going right to 90psi then down to 70psi and then it surges up and down ,there is just not even a close moment of smooth rate of gain.it is as much of a pain in the --- as over boost cut is.I am killing my oil and stuff with all this extra fuel so i am resting the car till i get this thing figured out,but like i say it is going to be a ARRR by the looks of things