XXO/BVGC '38 Chevy Coupe Build

[manta22]

I agree with Jack-- if this pump is only used to circulate oil to an external oil cooler, that motor and pump is serious overkill. Circle track racers use a mechanical pump that is belt-driven off a pulley on the diff yoke.

Regards, Neil  Tucson, AZ

[38flattie]

Gentlemen, this setup is not for an oil cooler!

Two stages will be used to dry sump the tranny, and two stages will dry sump the rear diff. It may appear a little big HP wise at first glance, but I believe it's sized right for the pump. It will have a battery dedicated to powering it.

[Rex Schimmer]

 The great thing about electric motors is that as long as you have sufficient amperage and voltage they will make alot more power than they are rated for also if their load is less than they are rated for the will only make enough power to carry the load. So with Buddy's dif/tranny pump the 1/2 hp will probably work great. Plus since it is a DC motor he should be able to regulate the pump speed easily. Buddy are you going to run the oil through a filter before going to the diff or trans? Like wise are you planning to run something different for lube than the standard 90 or 140 wt? Are you also planning some sort of spray bar to lube the gear lash and also the bearings?

Rex

[38flattie]

The filter system will be similar to the engine setup-there will be 3 micron filters on the return side, one each for the diff and tranny.

Yes, there will be spay bars, for cooling purposes as much as lubrication. I realize it's not a conventional setup, but I'm confident it will work.

I'm still contemplating the oil to use. I have a a bunch of the Mobile 1 Racing 0W-50 oil, I'm tempted to try. I've also thought about a straight 40W.


Any suggestions?

[SPARKY]

use the synthetic you have with a bottle of ProBlend gear additive  ProBlend is what GM used on the Corvette trans axels..

[38flattie]

Randy and I just got back from John K's. John is a fiberglass genius! The snorkel and hood scoop are all but done!


Next up, an 8" narrower front axle.....

[manta22]

Nice looking snorkel & hood scoop but have you considered how far forward it moves your center of pressure?

Regards, Neil  Tucson, AZ

[WZ JUNK]

Nice looking snorkel & hood scoop but have you considered how far forward it moves your center of pressure?

Regards, Neil  Tucson, AZ

Yes, we talked about that last night.  There is no way to do something like this without changing the center of pressure and it will now be forward of what it was previously.  However, we are looking at adding a spoiler on the rear with large spill plates which should help by moving the center of pressure rearward again.  I am hoping it will be more than a trade off.

John

[38flattie]

Neil, Here's a quick mock up from last night.

We did decide to move thing further 'outboard', and there will be more on this later.

[manta22]

Before you decide, it might be instructive to do some wool tuft testing to see where the airflow is that will make the spill plates more effective. Moving them out to the rear fenders looks like it would give you cleaner air flow. Maybe that's not legal-- I haven't read the rule book for your class.

Regards, Neil  Tucson, AZ

[38flattie]

Thanks Fordboy!

Yes, I believe we had every bit of 10% tire spin, one we approached 160 MPH. These cars have a large area under the trunk, that the car gets a tremendous amount of lift there. This is one of the things that we are working on for the comp coupe classes- a better bellypan to help os out, and better aero above, including a way to create some down force.

Thanks for the charts! At the moment, I plan on 6000 RPM as the upper limit. We'll test and tune on the dyno, with that being or max target.I think we'll be running 2.30 gears to try and hold the RPM's down a little, but will do what's necessary.

Of course, everyone knows how this works- if we're just a couple of MPH off of our target, that minimum will be raised to try and achieve the goals! LOL!

I'll pass this info on to Dema and John!

[38flattie]

Fordboy, I'm waiting for Dale to get you the weights. I have the rod and piston weights, but I do not have the piston pin and keeper weights.

Thanks again  for all of your input!

[38flattie]

38flattie,

Attached is a .pdf with gearing charts for the FlatCad.  There are 2 files which reflect the gearing as used in 2012, these 2 files show correction factors for the speed calculated Vs. the speed attained.   Is it possible that you have as much as ~10% wheelspin/traction loss?

There are also 6 additional gear charts that have various changes such as rpm limit raised, diff ratio change, tire dia change, close ratio trans change, etc.

Within these scenarios it appears that the maximum rpm drop is ~ 1900rpm, close ratio OR wide ratio, dependent on the rpm limit used.   It appears that the rpm drop could be as narrow as ~ 1600rpm, with the close ratio gearbox.

It would seem sensible then to modify/tune the engine for a workable powerband of ~ 1600rpm min. to ~ 2000rpm max.   I would attempt to achieve this by modifying the aspect ratio of the torque curve.   I would make changes that would rock/raise the curve from peak torque to peak bhp.   Peak bhp definitely needs to be defined, OR, an rpm limit based on parts stresses needs to be defined........     and the engine modified/tuned respectively.

I am sure you will have some questions after looking over the charts.   I am not so concerned about the predicted top speeds at this point in time, if only from the traction standpoint.   I think that is important to have defined the minimum useable rpm range, in order to properly modify/tune the engine.   More useable rpm range is better of course, as in flatter curves.   But the fact of life is that as an engine's output goes up in bhp/cubic inch, the useable rpm range becomes more narrow.............

Edit:  If you want to investigate other permutations, it is pretty easy to plug other numbers in to the program to see what rpm drops it spits out.  I used the info off your build diary.  Posts #1257, #1349 and some information you sent in a pm.  Let me know if you want me to run the 2.32/1.69/1.29/1.00 setup, but the drops will be in between the 2 other setups.
 
Fordboy

Fordboy,

Can you run the numbers with 5500 RPM, and 6000 RPM, 2.30 gears and 2.40 gears, and 28" and 29" tires? I think these combos and RPM's will cover our needs in all of the classes we will run.

Thanks!

[saltwheels262]

38,
Wow- to the additions on the body.

bf

[38flattie]

Fordboy, we learned our lesson about running against the rev limiter!

When I mentioned how we had run against it, Rex gave me a pretty good run down as to we we shouldn't- much the same as you're pointing out.

We won't make that mistake again!