Max boost on the log TI

[iTurbo]

I would like to hear opinions on max boost on the log TI motors ('85-'87 specifically)

Right now I have an '85 log TI engine installed in my '86 GLH Turbo. I'm using all the right '85 parts to go along with this (G-head/pistons, '85 LM, early distributor etc.)

I have the boost set at 10 psi with a grainger valve right now. I always run 91 octane without any ethanol (no 10% stuff)... base ignition timing is set at 12' BTDC. Injectors are stock replacements from Rock Auto.

Car is running pretty freaking awesome. I also recently added a ported head from a very reputable member hear and the car is now faster than ever before. The car also has full 3" exhaust (TU 3" S/V, no cat, FWDP cat back etc..)

Would it be out of the question to turn the boost up to ~12 or so? I have an Autometer narrow-band A/F gauge and it is pegged to the 20th light at WOT. I haven't heard one iota of detonation either. I know there will be a few guys out there that will tell me to get a wideband O2 gauge, but for this setup (which is more of a resto than modded) I feel like that is just overkill. I only want a little more boost. I know ~15 is out of the question but maybe 12 psi would be OK.

[GLHNSLHT2]

I'll be the 1st. A wideband is the only way to go. My old 10 light NB gauge was at 8 lights. I kept adding fuel. It NEVER went above 8 lights. Finally got a Wideband and threw it on the setup. Wideband pegged at richer than 9:1 a/f ratio's. I pulled 40% fuel out of the curve to get it back to 11.5/12.0:1 ratio's. The NB gauges aren't really any good other than telling you if you're O2 is cycling well at idle/cruise.

Think of it this way, $50 of that goes towards a new O2 sensor, the other 100-120 goes to the gauge. With the Innovate you can feed a simulated NB signal to the ECU and also tweak it a bit and fool the ECU into running the car a bit lean at idle cruise and the 1st few psi of boost till it ignores the O2. So you'll get MPG, and Power because you'll know exactly where you're at. Money well well spent. If it were running computer controlled stock boost I'd say leave it. But once you start messing with the boost level throw a wideband on it.

[iTurbo]

I hear ya Jay. I know a lot of people say the narrow-band O2 gauges are a 'waste', but it is nice to know/see your O2 sensor working and cycling which is worth it in itself.

Do you like the Innovate O2 gauges? I will have to start looking around for one. I didn't plan on buying one for this car considering I've already sold it to my older brother, but in the best interests of keeping the motor together I know you are right. I spent a lot of time and note taking making sure I built the motor just right (ring gaps, oil clearances, torque specs etc).

[Vigo]

Ill 2nd the wideband thing. I've broken pistons at stock boost due to AFR problems. You don't even need to modify your car for a wideband to pay for itself in the event that something ike a fuel pump, regulator, filter, injector, o2 wiring, etc fails. So, dont think of a wideband as being necessary 'above X psi'. It pays for itself the first time it saves you from having to take your engine apart over the failure of a $10 part like a pump strainer.

I experienced massive detonation @ 16 psi on a log with all stock timing. I have heard other people were able to run that without detonation. I would PM 4 l-bodies about it, i think he is the resident expert on fast log setups.

I would THINK that with proper fuel and timing adjustments you could probably go to 16 safely, or more if you want to go e85. :D

[GLHNSLHT2]

You can see the cycling of the a/f on the wideband as well, it's just more a couple tenths of a point vs half the gauge cycling. I do like the innovate stuff. I like it's adjustability and the way you can daisychain more stuff into the system if you want. It's a bit harder to set up than the AEM but if you have half a brain and take your time it's not that hard. Grounds are very very very important. I run 2 of the old LC-1 setups and have not had an issue with them EVER. But my grounds are all soldered and connected right to the battery. I did have an XD-16 gauge go on me but innovate replaced it free of charge even though I bought it from a person 2nd hand. Make your brother buy it if it's his car. :)

[cordes]

I would see what Sprayn'log has to say about it also. He's run some high boost on a log before using alky if I'm not mistaken.

[iTurbo]

I would PM 4 l-bodies about it



Yup, that's where this new cylinder head came from that the Omni GLH is now currently running. I have gotten a lot of help from Todd. I even have my choice of the DC intercooler or Spearco intercooler setup for this car, but I probably won't see much of it soon so..

Considering how well it runs now with 10 psi.....no knock...NBO2 at 'full tilt'.......I was hoping to up the wick to 12 psi. Looks like I should just leave it at 10 psi for now.

[Tbird232ci]

I ran 14psi with no issues. Had a FWD Stage 2 LM, a hacked off exhaust, K&N filter and a home made boost controller. I didn't have any issues until I added too much base timing.

[ShelGame]

The limitation of the Log T1 isn't the log - it's the suck-thru throttle body. If you get creative and change it to a blow-thru, I don't see why you couldn't crank up the boost as high as any other TM engine.

FWIW, the new Mercedes 2.0L GDI Turbo engine uses an intake that looks a whole lot like a log intake; just in plastic, and with no injector bungs...

[contraption22]

I've run over 15psi on a log T1 with a fairly crude water injection setup. I also used an enlarged throttle body.
As suggested above, I don't see why you couldn't take a later throttle body and make a mount to use it on the earlier engines.

[Gaboon]

I think 12 lbs was about as much boost I could run non intercooled and on 94 octane fuel without detonation....Way back when.

With a Spearco over the trans IC and additional fuel, I used to run about 22 lbs.
I think the best I ever ran with a log intake was 12.6 @ 118 mph with a 50 shot of NOS. Not too shabby I say.:)

[dwh4784]

I had mine set at 11psi, any more than that and it would start pulling timing. If you have access to a scanner you could use that to see if you have any more room for a couple psi.

[4 l-bodies]

Jeremy,
As others have stated from their experiences that about 12 PSI is about max with 91 non oxy premium without intercooling or alky. That was about it for me as well until it was intercooled. Then whole new ballgame.
Todd

[iTurbo]

Thanks for the input guys. I do have an OTC 4000E scanner so I will be hooking that up before trying to run more than 10 psi.

[Spraynlog]

With no intercooler, I ran into detonation around 11psi on gasoline, but that is on a swirl head motor. My plans for next year will be installing +20 injectors and running E85 without an intercooler. The log motor is air flow restricted, so adding 30% more fuel (E85) compliments it nicely, and the higher octane helps keep detonation controlled. Are you running a swirl head LM on your car?

[Keito]

When Jay built his charger he converted it to GLHS LM and added a blow through T body before the turbo.
http://www.turbo-mopar.com/forums/photopost/showphoto.php?photo=11205&title=img-0482-sized&cat=500

[dwh4784]

I was even using a DevilsOwn alky injection kit triggered at 10psi. IMO the issue was heat soak in the manifold, you can check your intake temps with the scanner also and it gets scary any time you have to park the car hot (pit lanes at the race track, waiting for your turn at the dyno). I once raced my car back to back three times against the same car, 2003 VW GTI VR6 6 speed. First run, we get to the track, tech in, wait in line, line up, he wastes me by countless car lengths. I say I want to park it for a couple hours and try again because it felt slower than I know it is. So second time, I jump out three car lengths and hold him off until the last second when he nips me at the line. It was so close we hot lap and go again, this time I only get about half a car on the launch and he walks away the entire time. All related to the heat of the engine, he ran basically the same et/mph each time. (That VW friend bought that New Yorker from me and is now a 5 speed turbo Caravan owner:p)

The one time I dynoed it I suffered the same issue. Got there and waited less than a half hour, got it on the rollers and the charge temp was 190*+ and it was pulling timing (detonating) at my normal boost setting, even off the scale rich on the dyno operator's wideband.

Sorry for the long winded post, just relating my experience with the non-intercooled log after using it as a DD/weekend warrior for 4+ years. Super fun on the street but that was about it. Under optimal circumstances it had great power, but once heat soaked it was noticeably slower and prone to detonation.