[JLMounce]

Oh a physical vacuum modulator, that's cool. As opposed to being commanded by an ecu.

I should have guessed that from the pictures on the first post. It's clearly visible.

What are you using for the intercooler pump?

[darbikrash]

It’s a Bosch brushless electric water pump, flows 6 Gpm.

[darbikrash]

So it was back to the dyno last Tuesday for round 3 of the blower wars. This time I think we got a decent outcome and I am very happy with the results.

There were several differences and upgrades from the last effort, where we were plagued by high speed miss issues which I attributed to ignition problems coming from the dual sync distributor. This is both puzzling and disappointing, as I have a dual sync on my ’69 GTO and have not had issues with it, but here we are.

The fix was to switch to an external crank trigger, and just use the dual sync to fire the coils and provide the cam signal. This turned out to be the correct move as virtually all my issues went away, and it was apparent from the first few pulls that this was a very different engine.

Originally, I had 3D printed all the crank trigger mounting brackets and hardware using a high temp material, but I discovered that one of the 3D printed parts (throttle body spacer) had softened during the previous dyno run and had loosened to the point where a bolt actually fell out inches from the throttle body intake. So I took all the 3D printed parts out of the motor and remade everything out of billet aluminum.

The plan was to start with the smallest (boost -largest diameter) pulley and work my way incrementally into the higher boost numbers.

We did not quite make the 700 hp number I was looking for, but the torque was just ridiculous.

So here are the results:

- 5 psi (lowest boost pulley) made 546 HP 5300 rpm w/643 TRQ
- 8 psi boost, made 611 HP 5300 rpm w/685 TRQ
- 11 psi boost made 656 HP 5300 rom w/784 TRQ.

These were pump gas pulls, after the last torque number we put some better gas in, ~100 octane.

After that, the smaller pulleys started to show belt slip, so we did not get any full pulls on the higher octane, but we did see a 817 TRQ number before the belt started slipping.

Next steps are to get some Grip-Tek pulleys, I’m kind of kicking myself for not buying a few and bringing them just in case.

Keep in mind this is a stock 2 bolt main block with a factory cast crank, and perhaps the worst flowing cylinder heads (cast iron 4X, untouched) possible, so I feel this is a great result and clearly with regard to torque we are reaching the limits of the factory block.

A better head with say 300+ cfm flow will make a bunch more power at lower boost due to improvement in restriction as compared to the 4X heads.

But the goal of this project was to see what could be done for the guy with cast iron heads and a stock bottom end- making power with cylinder pressure and not RPM.

This time I set up a different (identical) blower with the fuel rails mounted externally, just to test this configuration. It worked well and there was no difference between this configuration and the previous config with the fuel rails and injectors mounted underneath in the valley. Note the stock valve covers LOL.




Some data:





Partial pull with belt slip. Take a look at that torque number before the belt slip kicked in:

[RAIVJUDGE]

Definitely interested . Would love to do this to my 78 TA. Just have to figure out how to get a shaker attached to the top of the blower

[Baron Von Zeppelin]

Incredible results - Really incredible
Congratulations on your work !

[R 70 Judge]

Awesome job! Those torque numbers are ridiculous. Any car with this combo will be super fun to drive

[65 Lamnas]

This must be eyeball-flattening torque....

[73LeMans]

This would be my setup for my next build. Congratulations, but more importantly, thank you for all your dedication and hard work. This is a fantastic win for the entire Pontiac community.

[Baron Von Zeppelin]

* Reinforced seat mounting suggested

[JLMounce]

Those are fantastic numbers for this combo!

[gtospieg]

Turbo LS what?...Awesome to see what can be done to a real Pontiac engine.

[darbikrash]

I've had a chance to dig into some of the Holley EFI datalogs from the dyno session earlier this week, and though I'd post up some of the plots.

This shows engine vacuum at idle converted to inches of mercury. This is a pretty docile engine to have 17" of vacuum:



This one shows the total timing under boost, we were at 28 degrees for the entire time.

[JLMounce]

Thanks for providing these graphs. I think what this shows is the true potential of what this type of system provides.

At 8psi, which I think is a great baseline here and around where a lot of people would run the system, you are producing at or a bit over 600hp. Some would say, you can build a 600hp 455 for cheaper and keep it NA. That's true, it's only 1.3hp/cid after all. The difference here is that the blown setup is going to be far more docile around town in normal cruising. Yeah it's probably going to be more expensive going this route, but you get to have your cake and eat it too.

[darbikrash]

Originally Posted by JLMounce

Thanks for providing these graphs. I think what this shows is the true potential of what this type of system provides.

At 8psi, which I think is a great baseline here and around where a lot of people would run the system, you are producing at or a bit over 600hp. Some would say, you can build a 600hp 455 for cheaper and keep it NA. That's true, it's only 1.3hp/cid after all. The difference here is that the blown setup is going to be far more docile around town in normal cruising. Yeah it's probably going to be more expensive going this route, but you get to have your cake and eat it too.

Thanks for your feedback, and I agree.

The baseline run N/A with a carb made 419 HP, so the supercharger made +50% more power- with a disproportionate increase in torque. Not many 600 HP engines are making over 800 ft/lbs. which goes to the overall drivability and "seat of the pants" performance much more than HP.

One of these will be in a street car soon, so we will have some real world feedback as to drivability, which I expect to include instant boost, unlimited torque anywhere in the powerband, and the ability to use high (numerically) low rear end gears with no overdrive transmission needed for street driving.

Not sure yet of the cost comparison to get the same HP N/A. Pretty sure you'll not get the same torque regardless of money.

The TVS head unit is capable of over 1000 HP with the right combination- but that was not the goal of this particular build.

There is still more work to be done.

The limiting factor in this build was the cylinder head. On a good day, these (untouched) 4X heads flow ~205 cfm. On the subject of boost what you are really seeing here is better stated as a flow restriction- which shows up as measured boost. The name of the game is airflow not boost.

As a next step, a better flowing cylinder head is already in the planning stages.

Anyone care to speculate what this combo will produce with a 310 CFM head allowing 50% more airflow as compared to the 205 CFM 4X heads?

Stay tuned, but in the meantime the casting tooling is underway and I am working to simplify the ignition, refine the tune to make this as close to a thoroughly tested and validated system as I can.

[JLMounce]

I'd love to see it with out of the box D ports. I run a set of as cast KRE D-ports and they were impressive enough of a gain over my untouched #62's. Even at around 260cfm on the intake as advertised, I would assume 8psi would gross somewhere close to 700hp. In the real world I would bet on somewhere around 670.

[darbikrash]

Agreed.

In Post 103 above we showed a best of 657 HP (first graph) on the 4X heads with the pulley slipping. I'm confident that had we not had the pulley slip we would have touched 700 due to the higher boost. Those heads flow 205 cfm, give or take, and I would hope that a 310 CFM flow number would result in substantially higher HP at a lower boost number due to the lack of restriction.