400RWHP + 20MPG... How to do it??

mjbtv · Jul 23, 2005

Gears make the difference. A 2 speed axle would be nice.

diddylx50 · Jul 23, 2005

my car gets 8-10mpg around the city gotta love high stall auto's

I think 400rwhp and 20mpg can be done with the combo that you have stated and some tuning via a PMS or Tweecer

CrazyCobra · Jul 23, 2005

I think you are setting the bar to low. I am in the process of of building a car that will have the capability of 800+FWHP, easily get over 20mpg, and have to pass emmissions.
The answer is simple, turbo. Start with a 76mm garret GT42R good for 1000hp. Make it a 331 with the use of a dart block, and forged internals(I'll be using scat) are essential for the reliability. The AFR 185's fit the bill (for my self as they are emissions legal), and will flow enough right out of the box for even my goals. The 20mpg+ will come via a D&D viperspec T56(required for this level of hp to keep it reliable) and as it has a .5 sixth gear runnig 4.10 gears will still get great highway milage. This combo will require lots of fuel at WOT so a areomotive fuel system with a sumped tank will be needed and a set of high impedance 60lbs injecters are required. This can all be managed with the stock computer and the twEECer or the twEECer RT would be even better. The final and perhaps the most important part is the cam, a stock cam in a combo as described above will likely tap out at the 675-725hp range so i would recomend a custom grind, but keep it small to retain that solid torque down low for the highway crusing .
But if 400RWHP is what you have your heart set on, the base HP turbo set up with a 60mm turbo and all the parts to make it work as a turn key system makes in that area (433RWHP actually) for around $5000.00. And with a good tune(read consevative A/F ratios) you won't even have to upgrade block or heads or cam, as turbo's don't stress parts like nitros can.
Good luck with your qoals, and remember technology is our friend.
Steve.

MeanMussy · Jul 24, 2005

CrazyCobra said:
I think you are setting the bar to low. I am in the process of of building a car that will have the capability of 800+FWHP, easily get over 20mpg, and have to pass emmissions.
The answer is simple, turbo. Start with a 76mm garret GT42R good for 1000hp. Make it a 331 with the use of a dart block, and forged internals(I'll be using scat) are essential for the reliability. The AFR 185's fit the bill (for my self as they are emissions legal), and will flow enough right out of the box for even my goals. The 20mpg+ will come via a D&D viperspec T56(required for this level of hp to keep it reliable) and as it has a .5 sixth gear runnig 4.10 gears will still get great highway milage. This combo will require lots of fuel at WOT so a areomotive fuel system with a sumped tank will be needed and a set of high impedance 60lbs injecters are required. This can all be managed with the stock computer and the twEECer or the twEECer RT would be even better. The final and perhaps the most important part is the cam, a stock cam in a combo as described above will likely tap out at the 675-725hp range so i would recomend a custom grind, but keep it small to retain that solid torque down low for the highway crusing .
But if 400RWHP is what you have your heart set on, the base HP turbo set up with a 60mm turbo and all the parts to make it work as a turn key system makes in that area (433RWHP actually) for around $5000.00. And with a good tune(read consevative A/F ratios) you won't even have to upgrade block or heads or cam, as turbo's don't stress parts like nitros can.
Good luck with your qoals, and remember technology is our friend.
Steve.

Now, I REALLY want to hear how this combo turns out!!

Without a doubt, if I look for anywhere near 500HP at the crank, I'm going w/ a Dart (or similar) block and forged internals. That was the reason I was going w/ a 351W based motor, for the stronger block.

BTW, as for the TwEECer (I'll give a plug here), the RT is the ONLY way to go!! The ability to log real time is great!!!

custom89stang · Jul 24, 2005

Simple Answer

OK THERE IS A SIMPLE ANSWER HERE. Forget what everyone else has to say cause i read this in a muscle mustangs and fast fords magazine. The guy ran 15PSI of boost, with A TUNE, which is very important of course and no A/C and a few other deletes and he made (COMPLETELY STOCK 302 BY THE WAY) 380 some odd HP and 530 lbs of torque, stock cam, stock intake, everything, like i said...

custom89stang · Jul 24, 2005

any more than that would blow some gaskets probably, but if u dont stomp on it and drive carefully superchargers can actually help your car be more efficient, so technically you could prolly get 20+ MPG on the highway at least...

Car RamRod · Jul 24, 2005

bimmertech said:
put a turbo'd 302 based engine with 3.27 gears and a t-56.

I like this setup

NUTCASE · Jul 24, 2005

diddn't hot rod magazine do a thing a while back where they had a bunch of cars that ran 12's and got 20+mpg. notrouse cars diddn't count. there was a guy wth a s/c'd 347 that got it. there were also different cars running grand national swaps and 2.3 turbo swaps. either way, I think the only car that wasan't boosted was a f-body

dderek · Jul 24, 2005

i remember watching a compilation video of this greenish/blue lx hatchback. it had some sort of turbo setup. ~400-500rwhp. i forgot.
ran in the 10s.
it was SUPER quiet.
showed him at the track. then playing on the street with some classic red car, not sure what it was.

anyways.
in his video he said he'd get 28mpg.

it was called lxcomp5 or something like that.
ill have to dig it up

MeanMussy · Jul 24, 2005

yeah, dderek, if you come across that article, please post it up. that would be a nice one to read!!

Thanks!

vristang · Jul 24, 2005

I would like to throw out my thoughts.

Not mentioned yet is EGR. This will help the fuel economy and not hurt power at all.

I like the idea for the t56. I did some research a while ago and you can swap the sixth gear for a .56 (maybe .59?, don't remember).

Gearing is going to be very important for the mileage. Crunch some numbers to see where your cruising rpms will be with various combinations. It is easy to do and I can send you my spreadsheets if you wish.

For the power adder I would consider nothing other than a Turbo (or twins). Any supercharger will make the power that you want, and increase the economy if tuned properly, but a supercharger will also rob more power from the crank than a turbo. A turbo is by far more efficient than a supercharger. For the same level of boost you should be able to make more power with a turbo than a supercharger due to the efficiency advantage. Also, use an intercooler to maximize efficiency.

Another design factor is aerodynamics. Make sure that the stock air dam below the radiator is in place. You could also add smooth flat panels to the underside of the car. A nose piece that does not allow air under the car, and low hanging side skirts will help as well.

Tire width will make a difference as well. Wider tires will present more rolling drag, and decrease efficiency. Maybe just use narrower tires in the front? This will depend on whether you want a corner carver or a dragster.

Inside the motor there are other options.
Use an electric everything. Electric water pump, fan, oil pump, ... A dry sump system would be nice. Getting a crankcase vacuum pump will decrease drag on the crank. I have been looking for a way to get this vac. from the boost (turbo or supercharger), because it is energy which is already created.
Well I can't think of anything else right now. Hope I gave you some ideas for maximizing economy and power.

bcd · Jul 25, 2005

buy an 03 or 04 cobra. thats about it.

Boss 351 · Jul 25, 2005

How do you loose 100hp from the flywheel to the wheels... That would produce so much heat (power needs to go somewhere), it would melt the transmission and diff lol.

A very well tuned EFI system and boost would be the best bet. Low compression ratio and high boost. Don't forget to loose some weight... I see good mileage with my car (granted I'm far from 400hp). But I get to shift at 1500rpm in town and still be ahead of traffic.

vristang · Jul 25, 2005

Boss 351 said:
How do you loose 100hp from the flywheel to the wheels... That would produce so much heat (power needs to go somewhere), it would melt the transmission and diff lol.

.

What percent power loss is typical with a t5 and 8.8 limited slip?

I have never heard any #s on this, but I am sure someone out there can throw out an example of their motor on the engine dyno then the chassis dyno.

Boss 351 · Jul 25, 2005

People like to say 25% (100hp from 500 as said) but from some articles I've read they say 12.5% is a safe bet. I got mad math skillz lol so dammit even at 12% that's still a good 60hp converted to heat due to friction in the drivetrain and power used up for the rotating mass. I like to jump the gun

So if we use an aluminum driveshaft and flywheel with new joints and synthetic oil in the transmission and diff, we would have a more efficient drivetrain? I wonder how much power we can get back?

kck6894 · Jul 25, 2005

I am proof that you can get 20 mpg on the highway at 400rwhp. I run a N/A 347 in a true street form that makes 421rwhp. Yesterday I drove it and got 20mpg with the A/C on. It can be done and it is possiable.

MeanMussy · Jul 25, 2005

kck6894 said:
I am proof that you can get 20 mpg on the highway at 400rwhp. I run a N/A 347 in a true street form that makes 421rwhp. Yesterday I drove it and got 20mpg with the A/C on. It can be done and it is possiable.

Could you please share your combo? H/C/I, etc?

MeanMussy · Jul 25, 2005

Boss 351 said:
How do you loose 100hp from the flywheel to the wheels... That would produce so much heat (power needs to go somewhere), it would melt the transmission and diff lol.

A very well tuned EFI system and boost would be the best bet. Low compression ratio and high boost. Don't forget to loose some weight... I see good mileage with my car (granted I'm far from 400hp). But I get to shift at 1500rpm in town and still be ahead of traffic.

Assume: 15% drive train loss
500HP - 15% = 425RWHP
To one sig fig (since this is a rough estimate), 425RWHP ~ 400RWHP

kck6894 · Jul 25, 2005

347CI 11.25:1 COMP
PORTED TW heads
AFM N-111 CAM
VICTOR 5.0 INTAKE
42LB INJECTORS
90MM THB
POWER PIPE
80 MM PRO-M AIR FLOW METER
1 3/4 LNG TUBE HEADERS
3" X-PIPE AND CAT BACK
92 OCTANE PUMP GAS
4.56 GEARS

NUTCASE · Jul 25, 2005

I don't think the whole % thing on drivetrains is all that accurate. it might work out if you have say, 300hp. but lets say you put a 800hp motor on the same drivetrain. I just don't see how the same trans is now going to soak up like 70 more hp just becouse you got a bigger motor. same thing with the drive shaft. how is a ds that soaks up lets say 25hp on a 100hp car now all of a sudden going to soak up 100hp just becouse you went to a 400hp motor

400RWHP + 20MPG... How to do it??

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