[IT Manta]

It seems I have died and gone to heaven.

Am I reading this correctly?

It seems we have a competition adjustment in our favor. The 1900/Ascona and the Manta can now leagally use the 9.0:1 pistons and the GT intake valves.

On that note do the 40mm or 42mm intake valves create more flow in an unported head?

I know in the Volvo heads I have been working with the larger intake valves actually loose flow due to loss of velocity (no matter how the rest of the head is ported or the cumbustion chambers are modified).

 

[IT Manta]

Ok, I will take the head back to my machine shop for the larger intake valves. Are the L-joy seats common? Or will I need to supply them. Should I just get OE valves from Opel GT source?

I have a nice cam, and am using the 1.9 EFI. I was running a 32/36, but I feel the EFI provides better power across the board.

I have used a decent header and found them troublesome and too high RPM oriented. I am now using a sprint manifold with a custom made headerpipe merging into a 2.5" collector and 2.5" tubing all the way back to a magnaflow 4" round straight through muffler. The exhaust routs under the axle. Are you interested in pictures? The exhaust is off the car for my overhaul.

 

[IT Manta]

Yes, I agree a proper header would be the best way to go, but It is not a priority for me right now. I know the sprint manifold will be reliable for me ( no leaks ) and provide good low end torque which is desirable in a relatively low RPM IT motor.

There are so many colliding theories in the exaust path to really make general assumptions (I am not saying that you were assuming anything). I will be dyno tuning the EFI and will then compare output as I try different setups. Right now I am subscribing to the theory that after the header collector you want as little backpressure as possible. I did run this setup through 3 drivers school sessions and felt the car was running real strong (and then it let go!) and this was with the Weber.

This time around I have the ability to really gather empirical data to make sure I am going the right direction.

 

[IT Manta]

Definately appreciated Bob. I will proceed with caution. I have a spare EGT setup, but no real good location in the sprint manifold to test all cylinders at once. The EFI should be pretty even though.

 

[IT Manta]

The GCR clearly states that updated or backdating between a specific model is allowed as long as the update or backdate is done as a complete assembly.

We won the SF regional ITB championship in the eary 90's with a 74 manta that was converted to EFI.

 

[IT Manta]

TGSI,

The internals of the PSC1 piggyback unit made by Split Second www.splitsec.com will fit neatly with the existing ECU inside the original box. You may want to at least look into the specs of the unit. I have used this calibrator to re-map very modified cars with large injectors and larger MAF meters using a Motec wide band A/F meter and a chassis dyno. The best thing is that it only costs $250.

Also my 2001 GCR says that the factory ECU must be unmodified. At your convienience can you get me the wording form a current source?

 

[IT Manta]

The PSC1 version I use does not require a map sensor and has as many adjustable cells as any of the affordable engine management systems. The internals of the PSC is very compact. I opened up a 75 efi control unit and it looks like it will fit between the two circuit boards.

I think you are underestimating the tunability available with such a unit. I have experience in both stand alone EMS and these
"piggyback" units and can attest that the tuning for power is equal.

 

[IT Manta]

TGSI,

I have followed products by electromotive since Don Davendorf started the company in the eary 80's. I Know the Tec 3 well. You will still need to use the MAF meter from the L-jet, and the tec 3 is MAP/RPM based. The Tec3 also has full ignition control that is not allowed in IT. So what Electromotive product would you actually use? Maybe this is allowed in IT now, I am still waiting for my 2003 GCR to arrive. No doubt this is the way to go on your GT-4 car.

What feature(s) of a fully programmable EMS do you think are an advantage besides full control of the fuel mapping on an IT car?

 

[IT Manta]

TGSI,

I could not agree with you more on a couple of things. First that the IT rules are out of hand when they allow tons of money to be spent to make a winning car. That in itself is contrary to the class belief that is stated at the front of the IT rules. And also, yes the resolution of modern aftermarket EMS is far superior to the analog system used in early L-jetronic such as our '75 system.

Also it is possible that the Split Second piggyback sytem for a L-jet does need a map sensor (the Volvo hot wire mass sensors that I use do not, I will have to talk with the engineer) leaving us both SOL on this front.

 

[IT Manta]

Yes sir that's how it tends to evolve. If the rules are written properly they would cap the modifications possible.

If one wants to spend all that money they should build a Production or GT car so we do not have to sell the farm to be competative. Like that argument has never been made, right?