2TG-3T Hybrid Discussion

[Celica_73]

Solex are known for losing the venture too but since that has happen to before (2 years ago now) I've been checking them regular. I also double check it after pulling the carby apart and can see straight through to the venture. Dyno little expensive around here as only one in town. $170 a run plus labour and parts.

The operator didn't think the engine was averaging a lean enough mixture to be a problem. The oxygen sensor was at the end of the my exhaust pipe. It was very lean.

Anyone know how lean an engine need to be to shit itself in 200km? What i can't work out it took 6000 mile the first time blow up. Which seem to indicate something has changed after the rebuild.

[allencr]

Wow, you've really got something. Sorry. I think any carb/intake system problem would be very noticeable after looking at & comparing the plugs, same with ignition & cam timing for that cylinder, same with its cooling.

#1!!??WTF Nothing special except the coldest water & highest pressure from the pump, the hottest water coming from the back of the head, the short route for oil pressure(if the filter is in the front), and the harmonic/damper/balancer/WTFever pully. I don't know.
Did the combustion chambers look like they were burning the same, also did the valve heads & stems look the same?
Does that rod bearing look like its been pounded by detonation or different from the others? How are the mains, #1 compared to the rest?

I've never fooled around with a bent rod and its symptoms, but I'd think that it wouldn't let the rings seal very well right from the start, not a delayed reaction like yours or the final results, just low compression & scuffed up in odd places - on the piston & rod bearings.
Good luck.

[TheToyman75]

Jason,

Clearly you have something drastically wrong with your engine build/combination that is localised or worse for Cylinder 1. Atthis point anything past that is a wasted guess without at the very least detailed photo's of the existing set up complete, photo's of your carby installation and most importantly photo's on the original failed piston and the new one. Pictures of the combustion chamber and piston top should be taken BEFORE they are cleaned/removed and of course the spark plugs would also be a useful tool.

Ideally tho you probably need to take the vehicle to a workshop that is familiar with the engine and ideally one that does engine building AND dyno tuning. Its generally allot cheaper to pay someone skilled , than keep rebuilding it yourself given this issue is clearly above your mechanical understanding and fault finding (No offense - we all have our limits and it could be a difficault fault to locate)

Good luck with it as I feel your pain. Nobody enjoys the feeling of pokeage after a rebuild or conversion.

[TheToyman75]

Oh and BEFORE you start pulling anything appart - Do a leak down test on it to see where you are leaking compression and do a cooling system pressure test to see if it has been breached and since it only takes a minute to do I'd do a TK test to !

[Celica_73]

Ok this may sound like a dumb question what do you mean my a TK test?

Did some ringing around and found a guy 60km from where i live that has built these engine for rally cars. Engine place is call Goodman Engines. Seems to know his stuff plus a engine dyno on site to break the engine in one.

This seem to be my best bet as Toyman said this problem was everyone thats seen the pistons and cyclinder head (which is Reconditioner plus Dyno tuner) no one can work it out. So taking engine still assembled to this guy and hope to thing something.

Cheers for the help

[TheToyman75]

A TK test is a dye test that checks for combustion gas in the coolant.

[roadkill]

Hi,

No mention of a possible bent valve (though unlikely) but what about clearances on the cams. Have the shims been rechecked? All it would take is a wrong shim to have been used that would stop a valve from seating properly. No matter how unlikely it may sound it is a very easy thing to check and fix and you don't have to pull the engine apart to do it.

Good luck buddy, hope you don't have to strip and rebuild.

bEn

[Celica_73]

Roadkill as much as I'd like to say that's possible Already had checked them plus head wasn't touch from the first rebuild. Oh yeah if it was a valve it also wouldn't cause blow by like I have too

Engine has been removed from the car and taken it to Goodman Engines. The local performance engine place I've just discovered.

http://www.coffscbd.com.au/goodman.html

That's the only kinda website they have.

Tell me that's he has build the hybrid engine for rally cars in the past with no problems so will be interesting Fingers crossed it works this time!

[Celica_73]

Here are photo of the Cylinder 1 Piston first engine.

Engine still together and sending it assembled but I'll ask if they can take some photo of the current piston.

Cheers again for the help Although still no solution I'll post up what the guy thinks it is as soon as I know.

Jason

[GasedT18]

From the second photo - it looks like the valve missed the flycut and clobbered the piston at some point in time.

Now what would make a valve do that? What are the consequences?

[TA23 Racer]

Looks just like my 3TG turbo pistons, it's getting broken due to to much advance low down in the rpm range around peak torque. Mixture looks ok no 4 point scuffing on the skirt so it's not getting hot from a weak mixture.
What sort of timing numbers are you running?

Cheers Dave.

[Celica_73]

GasedT18
If your talking about the little nicks around the flycut thats not the problem as they were there before the piston were used from machinist. Even if it was hit valve i can't see how that would cause the ring lags to break that would more like bent valves or smash the top of then piston.

TA23 Racer
That piston falled with the time as static 14 and stopping at 26 at 3000 the flat. How ever current is 10 static and max at 20 at 2500, retarted incase timing was an issue dyno tuner says it need more advance but didn't want to give it any until the engine was worn in more.

[TA23 Racer]

Jas does the j-car have some load advance fuction to replace the vaccuum advance unit?
if your comp is around 10:1 20degrees @ 2500 might be to much when the engine starts to get into breathing at around 3500-5000. with those cams it will need advance under the effective rpm range just to get it going then when it starts breathing the advance needs to start retarding then when the revs get up the advance can start creep back in. the more efficent the camber, higher comp and the better the ports the less overall timing required

cheers dave.

[Celica_73]

Well the engine rebuild thinks he's found my problem. His done the compression ratio calculation and discovered it's currently 12:1. Way too high for street fuel. So going to drop the ratio back to 10.2:1 with a combination of machining pistons and head.

Cheers for the input guys.

[af300e]

Why drop it so far back? 10.2:1 is low. It will allow you to run gallons of advance at high rpm, but the low down power will suffer a bit, maybe more than a bit. 12:1 is high, but a combination of less advance (need to lock the dizzy, use computer controlled advance or, restrict the advance in the dizzy) and more fuel can help you out here. For what it's worth, and I know the application is different but the principles are similar, my YZ250F runs 12.5:1 and does not knock on 98. I've also run it on some rough bush fuel (95 or less) and even that can't induce a ping.
Mine is a 2006, 2008 YZ runs 13:1 on 98 unleaded. No knock sensors, no fuel injection.

Naturally, 13:1 is crazy, but you can no doubt get away with 11.5:1, so is 12 (with proper fuel and ignition tuning) really such an enormous stretch?

Many very mild (as in 9:1 static CR with 7-10 psi boost) turbo engines run an effective (not static) CR of up to 15:1. They overcome detonation by running rich mixtures and retarded timing. Maybe you could do go down to 11.5:1 and do some exprementation?

Another possible issue is that your ignition curve may be feral. Perhaps too much advance too early, and since most people spend a bit of time at less than 4000rpm (dunno how you drive, but since you're running it in..) you may be driving in that excessive advance stage of the curve quite a lot. That combined with loading the motor to run it in.....detonation.

Anyone built a motor with 12:1 for street use? If so, how did it go on 98 octane? What did your ignition timing curve look like?