Timing on stock EFI for 15psi of boost?

[Guest bastaad525]

Just wondering... been thinking of turning the boost up maybe if I finally get the car down to the track or whatever (finally got seatbelts YAY!). I run it at 13psi daily but I'm thinking of upping it to 15psi, with the RRFPR I definatley have enough fuel for that... I can make it pig rich at 13psi with the adjustment set only halfway thru it's full adjustment range.

 

Anyways, I'm wondering, on the stock '82 EFI, ignition timing is supposed to be set at 20* BTDC. I've always left it there even as boost has gone up and up, and never had any detonation on the dyno or on the road. But I was curious, for some of you other guys who have run high boost on stock EFI/ignition, did you end up retarding the timing at all?

 

The thing that sucks is, with this motor, you can DEFINATELY feel even small changes in timing, not so much when your on boost, but off boost the change in throttle response and 'pep' of the motor is very noticeable, so I'd like to leave it at 20* if that's safe. I've always relied on knowing that the stock '82 EFI was so conservative with timing and of course dumping it tons of extra fuel right around the torque peak of 3000-4000rpm, so I'm assuming I would still be safe. But if not, how much should I retard it?

[EZ-E]

I do know this though you are completely right in that any change in timing at all really does show a dramatic difference in how the car responds to throttle and off boost driving.

 

It is really incredible the difference proper timing makes with the L series motor. I know I had what I thought was a boos problem and what it turned out to be was timing even though the car idled well, its response was horrible.

 

I could not believe how bad it ran, and how it would richen up like a pig!. I found my timing was off 6 degrees retarded. Talk about being a miserable running vehicle.

 

On mine the timing is set to the stock 24 btdc and it is an 82 turbo.

 

Im running 13 psi on a T3/T4 with 36# injectors and it runs well there.

 

Maybe somone can chime in on how any adjustments might help. The only thing that I know for sure is advancing the timing slightly for a littel better bottom end off boost response does help but it isnt to well for top end and high boost.

[Guest bastaad525]

wow so 13psi on a much better flowing turbo, and still at stock timing. I'm not so worried then

[Brad-ManQ45]

Watch out - his is a better flowing and "cooler" turbo. The added heat from a stock T3 at higher boost may make a difference as far as timing goes...but probably just need a little more fuel.

[EZ-E]

Watch out - his is a better flowing and "cooler" turbo. The added heat from a stock T3 at higher boost may make a difference as far as timing goes...but probably just need a little more fuel.

 

 

Well we all know that bastaad has no problems at all with fuel delivery:P The T3 does max out at 15 and does run a bit hot, but with added fuel and concidering he has the larger injectors. I dont see a problem. My turbo died @ 180k, and it was running 15#'s for about a year and a half before it started to spit oil.

[sims76]

I've searched, but never found an answer to this question...

 

People always reference the initial timing when using the stock ignition because that is what you can easily measure. How do you know what that initial number corresponds to when you are at a certain PSI and RPM?

[Thumper]

I ran the stock timing 24 degrees on the ghetto beast when I dynoed it at 20psi spike then down to 18psi and had no pinging. This was with the not so great starion intercooler and I was standing right next to the engine so I heard nothing. When I upped it too 23 spike and 20 psi there was slight pinging above 5500rpms. On my new car I have run 19spike down to 17psi on the stock 24 degrees timing (83 ecu) with an npr intercooler with no pinging. I am going to run the car with 28 degrees with 15psi and see if it doesn't ping. I'm looking to get back my boost response. Also this is in houston, texas summer heat where we have 95 degrees with 50-60% humidity. This is without the heat index.

[EZ-E]

Thumper can you answer this though, as it is part of bastaads original question, and I was wondering the same thing. Any small amout of change in timing either retarded or advanced, is immediately noticed.

 

What is the cause of that as well? I know on my car, it affects all sorts, idle, boost, off boost speed, everything, LOL I couldnt figure out why my car was running so bad at the track and I lost a second off my times due to the fact that I the timing was inadvertantly retarded to much.

 

Sorry not trying to hijack the post just trying to find out how come timing affects these cars so much.

[Thumper]

Thumper can you answer this though' date=' as it is part of bastaads original question, and I was wondering the same thing. Any small amout of change in timing either retarded or advanced, is immediately noticed.

 

What is the cause of that as well? I know on my car, it affects all sorts, idle, boost, off boost speed, everything, LOL I couldnt figure out why my car was running so bad at the track and I lost a second off my times due to the fact that I the timing was inadvertantly retarded to much.

 

Sorry not trying to hijack the post just trying to find out how come timing affects these cars so much.[/quote']

 

I could answer that but it would go something like. Ummm yeah... it makes car go boom earlier in the combustion cycle so more boom and boom is good.

 

Seriously though the little I know about timing is this. Timing refers to when the spark is given in reference to what position the piston and valves are. When at stock timing the spark is given at a moderate amount of time after tdc. When you advance the timing it moves the spark so that it is closer to tdc. You do this so the combustion has more time to enflict its energy before it is released out of the exhaust valves. The down side is when spark is given so early that the piston is still on the way up or it is at tdc and the explosion sends it energy in a straight line instead of in a circular path. When you retard the timing it moves it farther away from the tdc so it has less time to enflict its energy before it is pushed out. Sometimes when the timing is retarded the combustion will be not completed by the time the exhaust valves are opened so it will continue out into the exhaust manifold raiseing temperatures. There are many other factors it also changes but I am not entirely sure about those. Anybody want to step in?

[wayne_in_KY]

I may be wrong, but I thought the stock timing for an 82 ZXT motor was 20 Deg. I don't have a FSM for the 82 turbo motor that I put in my 78 280Z, but I did see 20 Deg as the spec in the AutoZone.com web site.

 

Could someone with a FSM comfirm if this is correct?

 

Thanks

[mobythevan]

The down side is when spark is given so early that the piston is still on the way up or it is at tdc and the explosion sends it energy in a straight line instead of in a circular path.

 

There was a great article in one of my mags about when you want to apply the maximum cylinder pressure. You light the fuel off, then some amount of time later you get maximum cylinder pressure and you want the particular time to occur when the crankshaft has turned 90 degrees so the rod has the most leverage on the crankshaft. That was the rough idea. Of course all different fuel and mixture variables causes it to be more of experimentation to determine when maximum cylinder pressure is obtained. When you dyno tune in for that max hp number you should find out (assuming you could look into the engine) that you have moved timing to give you this relationship of maximum cylinder pressure to maximum rod/crankshaft leverage.

[Bernardd]

FYI I have seen dyno tuned timing maps for a 3.1 turbo stroker for race gas and they set the timing to above 30deg's until well into the 20psi range. Afr's were mid to high 12's. I also have the 91 octane maps for that car's dyno session. They dropped the timing to 18deg's by 15-16psi. Bottom line is you car really crank up the timing with good octane/intercooling/tuning.

[Guest bastaad525]

well.. I think I have the good intercooling part covered, at least

 

I don't have larger injectors, but I do have the RRFPR, which supplies a TON of fuel, enough to get the car richer than 10:1 at 14psi.

 

I went and checked my timing yesterday... I had forgotten where I had last set it, actually, I know I was experimenting with it back and forth a bit last year. I had actually had it advanced to 22* BTDC. After reading all the responses (thanks guys lots of good info here!) I decided to just leave it alone. I have also upped the boost from 13 to 14psi, and upped the RRFPR's fuel pressure a bit. It still amazes me how much you can really feel the difference from 1psi of boost... but then for anyone who remembers my old post about how much power/torque I saw gained from each psi when I was dynoing (average of 15hp/20ftlbs per psi)... I guess it should be no surprise. It's been cooling off a bit at night too so the motor seems to be loving that as well.

 

I didn't get a chance to hit the track tonite as was planned whenever I do though I'll probably just leave the boost at 14psi and see what she'll run... not expecting a stellar E.T. since I can't launch worth a damn, but should see trap speeds in excess of 208mph if the dyno doesn't lie

[EZ-E]

I found some articles on timing by one Mazda Miata member that put a lot into perspective, including how to do the math as well, it makes for a pretty interesting read.

 

http://www.miata.net/garage/KnowYourCar/S10_Timing.html

[cygnusx1]

I am running about 2-3 degrees + advanced over the stock 1983 factory spec. I run 14psi and got off the dyno with no ping to about 5500 rpm after tweaking the FMU to get it "right and safe". Sorry I cant be more specific with the numbers, it's late and I don't remember the stock timing for the '83 Turbo. I do know it's advanced initially over the other older years. The 2-3 degrees + made a huge difference in low end, off boost, torque.