The Road to Bonneville and back

[SIXPAK]

What does the truck weigh Peter?

[Plechtan]

The truck probably weighs about 3,400 lbs. For Bonneville we put in 500lbs of ballast for better traction on the salt.

We are getting ready to head down to Maxton NC for the Hot Rod top Speed Challenge April 2-3, 2011 You can follow our progress on twitter @Comanche_LSR3

[1bolt]

Awesome job Pete, I am just catching up and read the whole thread, been away from the forum for a long time. Great reading. I think it's awesome that you bested an SRT10.

So any plans to try and tweak more HP normally aspirated? I forget are there any aero mods you're allowed to do and it still qualify for the stock Comanche record?

At the HP/Gear ratio you guys are running aerodynamic drag, and oil pressure are consuming heaping gobs of HP.

Did you completely block off the front grill which reduces aero drag, believe it or not a huge amount of your drag C/E is air trying to make it's way through the engine bay and underside of a vehicle, I'm guessing belly pans are outlawed due to possible lift at speed, but keeping air out of your engine bay is as simple as closing off the grill, and locating the radiator lower to the ground with a electric fan on it.

I forget the exact ratio but every pound of oil pressure is eating up lots of horse power this is expressed as a direct percentage thing, like air temperature is. So the more HP you're making the more is required to spin the oil pump. I realize you want to keep the crank floating at some serious speeds, but there are lots of OEM sports cars that have normal oil pressure that can go 150mph on a semi regular basis (Cops and traffic permitting) while making 60 PSI at 6000 RPM's.

I'm not saying to take unnecessary risks, but 30PSI at idle seems like serious overkill. It's probably doubling the amount of HP required to turn your oil pump... and don't underestimate how massive a HP loss that can be.

Did you extend an air damn down nearly to the ground in front?

I didn't see a scoop on the front? Getting some ram air effect will reduce the resistance and temperature of intake air. A couple degrees of cooler air or a little positive "ram air" will make a rather significant difference. It's nothing special to a street rig, but at the HP and speeds you are going there's 50 to 60 horse power just by reducing intake temps by a couple degrees, or adding a few fractions of an inch of positive air depression.

If you're not allowed a scoop then use the grill area between the headlight and fab an air box that encloses your intake stacks much like a plenum... I wouldn't be surprise if given the horrible aero of a Comanche, that the under hood area is negative

You should make a few drag strip runs with a manometer probe and magnehelic guage in various positions on the hood and look for any positive depression fine reading magnehelic guages (you need one that reads in 1 inch or less of water) can be bought very cheap off ebay.

Drive line improvements might also be possible, for starters that ford 9 inch isn't just heavy (that was an objection someone had a few years back) but it also soaks a crazy amount of HP. Drag racers need the high shock load durability of a 9 inch, but you don't. I have seen Dyno graphs where the Ford 9 inch sucks 20hp over smaller drag race oriented rear ends, and that was a drag racing comparison... Some modular racing rear ends with less drag might free up a surprising amount of HP. Your rear just needs to have the right gear ratio and not over heat...

All drag gets exponentially worse as the HP increases and the peak HP RPM increases... this is partially why you saw such a bog going to 5th gear... I suggest trying to increase all your ratios and then tighten them up to the point where you need a pusher and some speed to keep the engine from bogging in first gear when you're already moving... This gets you gears that are closer together so that last shift is not such a tall one.

Lowering oil pressure, drive line friction and aero drag will help a lot at the speeds you're dealing with and getting 5th gear to be reachable there's a lot left on the table.

[donnie]

1bolt
I can answer a couple of your questions. A hood scoop is allowed, air dams, are not when running in production class unless they came on the truck from the factory.
Also when running production class you have to run the stock read end.
The only way you can block off the front grill would be from the inside so it can not be see in production class.
Most LSRacers run dry sumps oil systems for the exact reason you mentioned.

[Plechtan]

Hey just did an Podcast for Jeep news, here is a link http://www.jeepnewsnow.com/modules/news ... oryid=3373

[Plechtan]

Starting to work on the Comanche again, did not make it to Bonneville last year because of money issues. I ended up changing jobs, and things have been tight.

We gave up trying to set a record in the production class, the competition is a S10 with a Chevy v6 bored and stroked to 5.0L I has Brodix stock car heads on it, and i just can't get the airflow numbers high enough on the Jeep head to be competitive. Plan B is to go turbocharged. Target is 750HP we plan to go with a 4" bore and 3" stroke. Engine will run in the 7,500 rpm range. because of the short stroke crank, harmonics should not be a problem. I will post some picturs or the turbo install as we move forward.

[Plechtan]

I was able to get a block plate from Brown Dog that they use to make their motor mount brackets.

motormount.gif

With the turbo I will not be able to use stock motor mount on the drivers side. I removed the intake and exhaust to see where i could make the turbo fit.

Here is a shot with the Clifford intake in place. The turbo and exhaust plumbing will have to fit below this

intake.gif

I will need to have the intake machined for injectors and have a fuel rail made. I will make an adapter to put a large throttle body in the center, Probably something like 87mm .


here is a shot of the 3" stroke billet crank.

100_1822.JPG

[Plechtan]

Here are pictures of the turbo header flanges, they are made out of 304 stainless and cnc port matched to my head. The head in the picture is a stock Hesco aluminum head and you can see how small the ports are. looks like the same size as a 331 head. My ports are cnc machined and are 1.5" in diameter. The holes in the header flange are 1 and 11/16 with a 1 5/8 14 ga tube the inside will be be a little bigger than 1.5"

header-flange-1.gif

The flange is made in 2 pieces, the center stud is used on both flanges

header3.gif

Here is a detailed picture showing how the flanges overlap each other on the center stud.

header2.gif

[Plechtan]

Believe it or not things are moving along. I got the turbo in and here are some pictures

turbo-front.gif

turbo-rear.gif

turbo-side.gif

This is a Midframe turbocharger with the 76mm compressor wheel and the 75mm turbine wheel and a 1.14 a/r turbine housing. It has a billet turbine wheel. The engine will actually not be a stroker, it will be de stroked to 3" but will rev to the 7,500-8,000 range.

[Plechtan]

Here is a copy of the sheet i got from turbonetics

Untitled.gif

Here is the PDF

turbo specs.pdf

[GoMopar440]

It's amazing to see how far you're taking this engine.

As competetive as LSR records are though, it's probably going to be the only way to make it into the books. Can't wait to see how well you do over there.

[Eaglefreek]

Here's an old Rambler with a turbocharged 4.0. It might give you some ideas for routing the turbo. http://theamcforum.com/forum/turbo-ramb ... l?KW=turbo My only concern is how close the exhaust is to the intake.

[Plechtan]

Thanks for the ideas. Right now we are planning on having the turbo flange centered on the engine( front to back) and probably at around a 30-45 deg angle. the center two port pipes will actually come up wrap back down to the flange. the engine will have 2, 3 cylinder intakes with separate throttle bodies. This will give the room th bring the center exhaust pipes into the turbo flange. The drivers side motor mount has been lowered by about 4" to make room for the turbo. I will post pictures when it is done.

By the way, currently there is no record in the class we want to run. that does not mean that somebody else wont show up, but if nobody else does we will have a record. Our goal is to exceed 200mph