For new car, never run so no prior baselines. How to make a first guess.

Wt ~ 2800#
Since the car has never run before and there is no reference for a baseline, how do I get a good first guess?

Wt ~ 2800# (actually hoping for lower but don't know what I'll be able to get to)
Gear = 4.86:1
Tires = 29.5 x 15.50
HP ~ 550 @ 6000
TQ ~ 560 @ 4500

Thanks - Greg

 

When I had my TC build the shop had me fill out a form. They asked:

Vehicle WT
Peak TQ RPM
Gear ratio
Tire size

Then they build to specs. I'm running 2500-2600 stall. I'm sure there is an on-line calulator to figure that stuff out. Call a couple vendors and see what they recommend.

 

If this is just a drag car, id start at 3000-3200 stall and go from there. The guys in the Drag Racing section would know for sure what to recommend.

 

If its just a drag car, I'd go 4400 for yours. :cheers: All of the torque, and a lot of hp.

I'm not sure how your supposed to do it, but this is how I did mine:


This is a desk-top dyno of my car of what I think it actually should be making if everything was perfect. I'm not making nearly that much power though, maybe someday.

I picked a point under 3,000 rpms because I decided that was the cut-off for my street use. I decided to go as high as I could because the torque curve is pretty flat up until 3500 rpm. I wanted to get as close to the hp as possible.

I decided on a 2800 stall, because for the cheap converters I was looking at, 2400, 2800, and 3200 were my options. Since my car does make more torque than the 2800 was tested at, I flash stall to 2950 rpm. I'm still having problems with shift points, so I haven't gotten to test it totally, but for the most part she REALLY gets off the line quick, or will just roast the tires, depending on launch technique.

My car shifts at 5,400 rpm(ideally, the governor doesn't do it yet, I have to do it manually), so when it shifts, I stay over the stall, so the converter never unlocks.

Thats how I chose to do it, so far I'm pretty happy with it, I could have gone higher and stayed streetable though, if I ever get real heads/cam, I think I'd easily go as high as 3500 and still be streetable.

Cheers. :seeya


[Modified by NoWorries, 4:47 PM 1/3/2003]

 

I don't know squat about torque converters...

but I know a little about trannys... and I am curious why you chose a 200-R4? Isn't that the tranny in the old Buick Grand Nationals???

I figured a TH400 woulda been better?


[Modified by bogus, 10:29 PM 1/3/2003]

 

I meant to ask that too. The 200R4 is a good transmission for street cars, because they can be made really strong, and still have an overdrive.

If you had a built one already, I'd go with it, but I think it'd be more economically feasible in a race car to go with a THM400 or even lighter at your power levers, you could go built THM350.

Just my opinion, obviously I don't know much about building really high powered cars, the closest I've come is a ZZ502 at 555 hp/605 tq, but we just used the factory THM400, because we already had it, no real option there.

 

The 2004R is a good choice and holds up well in my car. I freshen it up every three years, but hasn't broken in 6 years. The tranny runs in the 9's with lots of street use. I shift mine at 6,600 to 7,500 RPM depending on boost level and even has a trans-brake. I have an Art Carr 3,500 stall, non-lockup converter bolted to it.
I surprised more people don't use them because of the overdrive/ street-ability, but I guess old habits are hard to break.



[Modified by TurboVette, 2:15 AM 1/4/2003]

 

TurboVette,

I read your trans install, it sounded complicated. Looking at the bottom of a C4, there isn't a lot of room for modification. I had a heck of a time with my drive-shaft loop, let alone a cross member.

I agree though, it does seem like a great transmission. I've seen more GN's doing wheel stands than any other car, and to see one launch really hard is incredible.

If you don't mind asking, how much did your 200R4 cost built? My buddy with the ZZ502 mentioned above got his 400 built to handle 800 lbs of tq for $1019. It seemed like a pretty good deal considering my 700R4 is rated to 550 lbs of tq for $1008.

 

I've alwas heard for race applications to pick a stall the is equal to your peak torque RPM, which looks like yours is 4500.

 

Yes, 200R4's were used in GN's.

The 200R4 has a different (lower) first gear than a 700R4. If the right version is selected and if money is spent to prep it (replacing the parts that are known to break) then it can be a durable, superior choice for a transmission behind fairly powerful engines.

I intend to use one behind a mild BB in a 3400 lb car that currently has a TH400. The car has 2.73 rear gears and the tallish first gear of the TH400 is less than ideal for the application.

Regards


[Modified by Slalom4me, 9:59 AM 1/5/2003]

 

Actually its taller, the 200R4 is 2.23 where-as the 700R4 is 3.06. I think one of the primary advantages for the 200R4 in drag racing is the close-ratio gears. Where-as a 700R4 shifts from 3.06>1.63, the shift isn't nearly that dramatic in a 200R4, I'm not sure of the 200R4's second gear though.

 

Call your trans/converter vendor and take thier advice.

 

You are right about it being taller. It was about 2:00 AM when I posted, I didn't get out the numbers and I must have been thinking about the 200R4 vs the TH400. (BTW - now that I have the numbers in front of me, my info on the 200R4 1st gear is different than your's - maybe you can let me know which version came with that 2.23 1st gear?)

Here are the ratios for the different GM boxes (hope this displays well)
________PG (2sp)_____350____400___200R4__700R4___4L 80
1st_____1.76_or-1.82___2.52___2.48____2.74___3.06____2.4 8
2nd____1.00__________1.52___1.48____1.57 ___1.62____1.48
3rd_____n/a__________1.00___1.00____1.00___1.00___ _1.00
O/D____n/a__________n/a____n/a_____0.67___0.70_____0.75

This is an advantage in other forms of performance besides drag racing. In my case, I expect drag to be a factor in the upper gears and a closer ratio should help the engine to stay within the powerband. The taller O/D of the 200R4 will permit me to maintain a similar final ratio while having a significantly lower 1st gear ratio (compared to the existing TH400/2.73 final gearing) by changing the rear ratio to something numerically higher.

Again, sorry everyone for suggesting the 200R4 1st is lower than the 700R4.

Regards


[Modified by Slalom4me, 5:47 PM 1/5/2003]

 

The "best stall" speed depends on the application and torque/hp curve. A high stall will be very mushy on the street but best at the strip.

As you likely know, for the strip you want to launch as high in the power band as possible and yet be above the stall RPM after each shift.

Of course the size and configuration of the TC are also important for maximum performance.

Give Grant of Grant Transmissions in CT a call (# on my site); he may be able to help and he can ship a TC.

 

NoWorries, there was lots of room for the 2004r. I'm not sure the cross member is necessary if you connect the "C" channel from the rear up securely. For a drive shaft loop I just welded a piece of aluminum on the "C" member to close it up. Other people in here are correct; you must throw some money at the 2004r to make it strong enough. It will cost more than a th400 to build up, but still cheaper and lighter than putting a Gearvendors O/D on the back of the th400. An additional advantage (other than the OD) is that its gears are closer together and you stay in your power band where the 700r4 has a long drop between 1st and 2nd. May I suggest you contact Bruce at Performance Transmission; he specializes in the 200's. He's a long way from me but it was worth it. http://www.ptsnctb.com/


[Modified by TurboVette, 9:22 PM 1/5/2003]

 

Thanks everyone. I chose the 200-4R due to the better gear spread (closer) than the 700-R4, and I want'ed the OD for street use. The 200 is also physically smaller, which helps in my very cramped cockpit space.

I've been reading a lot from Bruce at PTS over on the Turbo Buick board, as they have really worked on the 200-R4. At "list" prices I would definately go with the PTS unit. The Art-Carr sale (about 1/3 off) is enough that I'm trying to investigate that as an option.

I plan to discuss the converter with the trans people, but like to have a smuch background info as I can ahead of time. Right now I think I'm narrowing in on around 3500 stall for a 9" lock-up converter. If it looks like the Art-Carr sale is a good bet, then I'll order one fairly soon for the $$ savings. If not I'l probably wait thill Im closer to actually needing the trans (car has a "little" work yet before it will run :lol: ) ang to the PTS route.

Thanks - Greg