2TG-3T Hybrid Discussion

[petergoudie]

Is there any chance the conrod is around the wrong way? They can sometimes be reversed from original.

[jeffro ra28]

thats a hadny engine mate. Those are impressive figures.

Who's workshop was it dynoed at?

[SeptemberSquall]

could be making 96kw
ed's made 96kw atw with 1810cc, cam profile 310/288 256/[email protected], .414/.395', 10.5:1 compression and weber 45DCOE.

[GasedT18]

Good it's sorted.

So to sum it up the pistons and valves were colliding "the valves were just touching the piston". "Just"?

Just enough to smash up the pistons but not enough to feel via hand turning the engine in a test fit?

Did the engine builder not check with the old plasticine interference technique? It would have prevented a lot of expensive grief.

Wasn't there a noticeable clatter when the engine was run?

I've heard that it is advisable to remove sharp edges in the combustion chamber (to avoid hot spots that could lead to detonation) and the edges of the valve reliefs on the piston might do with some rounding?

D

[jeffro ra28]

Since this has happened twice on a said good setup.

Please answer one question for me.

Was the engine dummy assembled by you or your machinist prior to machining/flycutting the pistons? both builds?

Ok the dummy fit and machining was done by the engine conditioner.

Piston from last destroyed engine pictures included as you might be able to see the valves were just touching the piston.
Jason

Did the engine builder not check with the old plasticine interference technique? It would have prevented a lot of expensive grief.

LOL...................

[TheToyman75]

Ok Good news Engine is running and producing pretty good power.

So quick update
Cams used are Camtech Profile 401A
Current CR is 10:1.

Piston from last destroyed engine pictures included as you might be able to see the valves were just touching the piston. There are also photo of the the new piston machining used in current build beside the old cracked piston.

Current results from the engine on the dyno
Max power was 151bhp @ 6500
Max torque was 140ftlb @ 5000

rpm bhp tor
2500 52.1 109.4
3000 66.4 116.2
3500 82.2 123.8
4000 101.5 133.5
4500 119.1 139.4
5000 133.4 140.2
5500 139.6 133.4
6000 149.7 131.6
6500 150.9 121.9

Those interested final carby jets were MA 170 M 135 P 60

Cheers again for all those who gave advise
Jason

Jason,

The first set of cams I had in the pornstar were that exact Grind and they have an awesome midrange performance, they pull really well. I'm sure you wil be stoked with the performance. The pornstar was only 9.8:1 comp and didn't have any real headwork so its good to see the portwork on your head has paid off with a great result.

Grind No...Advertised Duration....Duration.................Cam Lift
......................@ ×010²..............@×050²
.................IN.........EX.............IN..... ........EX.........IN........EX
401A.........293°......293°..........242°......... .242°......372².....372²


That cams best result for me was a 91.7rwhp for Dyno Day 2. The next cam I used was the Camtechs version of the Cosworth L1 Race Cams. 240 degrees at 50 with 410 thou lift. Sure they made more top end but the midrange really suffered, there was nothing below 4500RPM with the big cams and it was nowhere near as much fun to drive.

[jeffro ra28]

Rod, all that where different with the cosworth cams was the lift? and a tiny bit of duration?

[Celica_73]

GasedT18
The valve on pistons on the Second rebuild ONLY and no that wasn't the cause of the problem! The cause was the high compression ratio as stated already. Turned out the my first engine reconditioner didn't supple the head to the machinist so there were unable to see the size of the valves or the angle and just machine them to the specs he gave them. Reason i know this as the machinist was the Goodmans Engine who rebuilt the last time. Also engine assembly was done by myself the first 2 times and no you couldn't feel pistons hitting valves and the main reason the pistons were hit valves was because the the reliefs weren't deeper enough and cams were unable to be dialed in correctly we knew they were close for that reason and made sure we had 0.080" clearance at TDC on overlap but they were touch 10 degrees BTDC on overlap. Yes there was a tappered noise from the engine and that what we thought it was shims not valve!

jeffro ra28
Engine was assembled and dyno at Goodmans Engines

TheToyman75
As you know this was your head and the valve grind I did get from you too. Overall I'm happy with the engine and glad it's finally working. Turned out it was the head work from your head that gave me some of the grif as it had been shaved done to a 60cc chamber. Also the machine the Chamber a bit more to help increase the flow after sunking the valves. The valves protruded into the bore so they sunk the valves back into the head more and also machine the top of the piston to reduce the compression.

Another quick question Goodmans also stated the vacuum advance need to be disconnected due to the cams. But as I'm running a Jaycar Kit and a map sensor does this still apply? I understand the Vacuum advance isn't any good at idle manily from the overlap in the cams but the jarcar kit I can select at what RPM and vacuum and how much it advances or retards. Is there any advantage to Vacuum advance on a modified engine?

[TheToyman75]

Jason,

I didn't use to run the vac advance on the pornstar but I also had the dizzt recurved to suit the engine. Your ignition curve should really be set on a chassis dyno when you get the car tuned.

[Celica_73]

Cheers Rod for the reply. The dizzy was remapped using the jarcar kit on the engine dyno and the map was what created those results but it has an options for a knock sensor and a map sensor, so just looking to see if a map sensor is required or a good idea thats all.

Cheers

[SeptemberSquall]

personally i don't see why you'd disconnect the vacuum advance
under cruise conditions (sustained throttle, moderate/high vacuum) the vacuum advance should help improve fuel economy
at idle the vacuum advance should not be having a major effect i would have thought...

edit:

from "how to build and power tune distributor type ignition systems" by des hammil

For virtually all road applications, (vacuum advance) is necessary and should not be removed...vacuum advance does is to advance the point at which the spark occurs when the engine is not under, or near, full load. While an engine may require 35 degrees total ignition advance.... it can certainly tolerate 45 to 50 degrees when under partial load and this amount of advance gives better fuel economy.

The improvement in fuel economy can be as much as 20 per cent and seldom ever less than 10 per cent.

For road going engines, vacuum advance is necessary and desirable and there is no real disadvantage in having a vacuum advance distributor on a high performance road-going engine, provided the distributor is in a good, servicable condition...

[RyleyMA61]

so, with big cams the exhaust side valve reliefs need deeper flycutting??

perhaps that is why grant (GW's) hybrid munched a valve and piston all those years ago? fascinating

[Born-Enthusiast]

just a question mate your damage looks very very similar to mine when I built my hybrid the problems I faced were piston 1 and 3 retaining the same damage as yours. We initially thought it was valve hitting piston and ruled it out as the plastacine test done by my machinist didn't even touch the plastacine. My engine was a result of detonation from incorrect tuning. I also have a high compression ratio guesstimated at around 11:1 or more and my timing is now set to 0 static and 25 total advance. why did you lower the compression of your engine by so much?

Also what fuel where you running? Im running the 98octane level fuel and got the dyno done to that. My rebuild has not had any issues with this fuel, timing and compression combination. The other problem I was experiencing was a lack of fuel being pumped to the engine by the stock mechanical pump. I'm fixing this issue now but this also lead to drastic leaning out and nearly blew my engine a second time. you may want to look at your fuel system and see if it is causing a lean out from running your resevior dry. you can see the damage done in photos in my thread here http://www.toymods.net/forums/showthread.php?t=23375

hope this helps

[SeptemberSquall]

. I also have a high compression ratio guesstimated at around 11:1 or more

wft caution?

[jeffro ra28]

compression ratio guesstimations are like HP guesstimations.....LOL