Superformance Coupe

[adeelmd]

Hello All-
I Am New To Clubcobra.

I Traded My Superformance Cobra ( 408 Stroker With 500 Hp And 5 Speed) For A New Superformance Coupe Which Will Be Ready For Pickup Soon.
It Will Have The Roush 427 Engine With Full Open Sidepipes And A 6 Speed. Just Wanted Anyone Out There With Coupes Or Experience Driving The Cobras And Coupes To Offer Any More Feedback From Older Posts As To How Does The Coupe Drive Compared A Similar Cobra Setup And Any Peformance Figures And Dyno Numbers For The Coupe With The Above Setup.
Thank You

[rcweingart]

Does your engine have a carburetor or DFI? The carburetored motor isn't as tractable at low RPM as the DFI engine. The DFI has a slightly better HP and torque curves but both are fun. There are a lot of little problems that you will be addressing once you've got the car so get on Peter Brock's Coupe Group list as there is a lot of information about the SPF Coupe available from the other owners. The March issue of Road & Track has an article about Peter's car. The performance figures are 0-60 in 3.5 sec, 1/4 mile in 11.8 seconds at 122.4 mph, 1.07 G. lateral and it set the R & T slalom record for a production car at 76.6 mph. Peter had sticky Kumho tires for the test and his engine is a 427 RDI with a 850 cfm carburetor producing 566 HP and 563 ft-lbs of torque and a Tremec T56 6 speed. My Roush 427 DFI engine has 580 HP and 542 ft-lbs of torque with a TKO600 5 speed. It drives just fine. Candidy, I think better than Peter's in regular traffic, especially stop and go freeway driving where I can let my RPM's drop to 1500 RPM or less and not have to down shift when traffic starts up whereas it would be bucking if it were carburetored. Back to trannys, Dennis Olthoff recomends the 5 speed over the 6 speed as it shifts faster, smoother and is stronger (and lighter), especially for track events but owners with blue printed 6 speeds (like Peter) like their trannys too. I feel you really don't have need for 6th gear unless you are doing long distance driving and want to drop the R's but I'm only pulling around 2750 RPM at 80 mph. Roush set the rev limiter on the DFI at 6200 RPM but, once my warranty has lapsed, I'll reset it to 6500 Or 6600 RPM which is about all you want safely before valve float in my opinion. You can do the numbers what my top speed could be (180 - 190 mph) which is more than adequate for track or street.

Hope this helps,

Ron Weingart

[adeelmd]

thank you so much for the info ron.
my engine will be the carb version (eric at dynamic told me the injected version had some reliability problems- and the carb version was just fine) - i saw the 8 stack version on the dreamcar garage segment and heard of its benefits at lower rpms and would put it in my car but trusted erics opinion and seemed like he was not after just making a few more dollars. i chose the 6 speed only because brock uses it and many of the test cars in the magazines had the 6 speed. my salesperson tried to convince me to go with the 5 speed which is lighter and i think less noisy? i guess i felt if its good for brock then good for me as i am not an expert. but sounds like either version of the engine and trans are great. i will not track this car and will not use it too much in heavy traffic areas. eric said the engine loses a little hp because of the shape of the low hood and the configuration of the short air intake. not sure how much the open sidepipes also cheat some hp. will the roush 427 have a rev limiter or do i have to ask eric to put one in? how do i get on that brock coupe list to help deal with small problems? my car is #102

[rcweingart]

Hi. I do not know of reliability problems with the DFI per se if it is properly installed. There is a lot you can do to tune the DFI as you can map the engine for performance, ecomony, etc. Peter has the 6 speed because his is an early car even though it is #73. My car is a late car even though it is #51. SPF used to let the owners pick their numbers but not anymore. Dennis Olthoff is the SPF's premier dealer/installer. He and his dad Bob helped develop the coupe (as well as the the GT) . Yes, the T56 is noisier and not as smooth or quick shifting as the TKO600 which is why Dennis installs just about only TKO's now. However, if you are going to install the T56, have it blue printed. Peter's T56 is blue printed too. I'm not sure what Eric is referring to by low hood and short air intake. I understand that most carburetored cars are using Victor Jr. intake manifolds and the package fits nicely under the hood. (BTW, Dennis cuts down the engine mounts to lower the engine about 5/8" and lowers the tranny about an inch to line up better with the driveline. I followed Dennis' lead and my installation is very clean.) Is Eric comparing the Victor Jr. to a tunnel ram or something? If so, yes, the Victor Jr. or any other single or dual plane intake manifold loses HP to a tunnel ram which is a high rpm intake that suffers at low rpm. For your street application the Victor Jr. or similar intake manifold is more than adequate. What are you using for a carb? A Holly double pumper at 750 to 850 cfm is just fine. Many people over carburate their engines and the engine bogs down under heavy acceleration as the intake velocity drops due to the large barrels. You will probably pick up, not lose, HP with the open side pipes. I have the rear exit pipes for their quieter sound level but am getting open side pipes and will evaluate the difference in sound level and performance beforfe I decide which to keep on the car. The coupe comes with an MSC 6AL ignition wired in. The 6AL ("L" for limiter) uses plug in modules (white plastic electronic modules about 3/4" x 1/2" with two prongs that plug into the box) to limit the R's. You can buy the modules at any speed shop. They come in packages of about 5 modules in, I believe, 200 RPM increments so get a set from 5500 RPM to 6500 RPM and use the 6200, 6300 RPM module while the engine is under warranty and use the 6500, 6600 RPM module after your warranty has lapsed. As for getting on the Coupe Group list, give me your email address and a little bio about you and your car and I'll introduce you to Peter by e-mail so he can add you to the list.

[adeelmd]

well i just talked to eric at performance engineering.
he agrees with you and olthoff- the 5 speed t600 is a better choice so i changed my order from the 6 speed. is the 6 speed only necessary for going 200+ mph?? what are the max speeds in each gear for your 5 speed? the car will have a holley carb but i am not sure what type. just added on the rev limiter also. i will try to find out more details once he begins work on the car. thank you so much for your help.

[rcweingart]

For me, yes, the 6 speed is for only going 200+ mph and for long trips where you want the rpms to drop a bit and for mileage. You can get a TKO 600 5 speed with a 0.62 5th if you want to go over 200 mph but the 4/5 split is terrible and all you really have is a 4 speed with a long overdrive. Here is the gearing chart from the Second Strike Gearing Calculator for what you will probably end with. Figure on 6200 rpm until warranty has expired and then 6500 rpm. As you can see, top speed at max rpm is 180 - 195 mph assuming you can get up to max rpm. My DFI engine reaches peak HP at about 6200 rpm so based on that and the Cd, I figure that I'm good for 185+ mph should I want try to go for bragging rights which I don't. My car is set up just fine as a high speed GT, A/C works fine, remote door poppers (both doors and hatch), stereo and I put in power windows (major undertaking). Easy to drive, great on the track, and an eye catcher for all those who see it.

The forum won't let me format the columns so the numbers don't line up well but you should be able to figure it out.

Tremec TKO-600 5-speed (0.82 5th) with 3.46 gears and 295/45/19 tires
Speed (MPH) in Gears at RPM

Gear | 1st | 2nd | 3rd | 4th | 5th
Trans Ratio |2.87|1.89|1.28 |1.00|0.82
Overall Ratio|9.93|6.54|4.43|3.46|2.84
Split 1.52 1.48 1.28 1.22
Rev/Mile |6,998|4,609|3,121|2,438|2,000
1500 | 13 | 20 | 29 | 37 | 45
2000 | 17 | 26 | 38 | 49 | 60
2500 | 21 | 33 | 48 | 62 | 75
3000 | 26 | 39 | 58 | 74 | 90
3500 | 30 | 46 | 67 | 86 | 105
4000 | 34 | 52 | 77 | 98 | 120
4500 | 39 | 59 | 87 | 111 | 135
5000 | 43 | 65 | 96 | 123 | 150
5500 | 47 | 72 | 106 | 135 | 165
6000 | 51 | 78 | 115 | 148 | 180
6500 | 56 | 85 | 125 | 160 | 195

[Woodz428]

My opinion is that Eric can't properly set up a DFI, and may use the reliabilty issue as a way to avoid having to deal with them. I know of one in particular that he set up that is still not correct...after 2 years and I don't even want to think about $$ spent since.

[LHoboken]

Hi Guys,
Really good information in this thread as I am trying to decide on what engine to use and who to let build the car.
rc, you really have a spectacular setup and that would be my choice if money was not a factor, I am trying to decide on the Roush 427IR or someone else's 427 like RDI or Keith Craft, or Performance Engineering.

Build seems to come down to getting Dennis to do it or go close to home and let Eric build it. I would let Dennis do it, but I want to see things as they progress if possible. doesn,t everyone use Dennis' ideas on their builds? Or does Dennis have so much experience he has the best ideas?

Thanks for the input guys, rc, I met Pete a couple of years ago as he was traveling the midwest and we talked about the coupe, if you could give him my email, perhaps he could set me straight with my chioces.
He will remember me from Mid-Ohio as I am the guy selling my BRE inspired 71 Datsun 240Z to buy my BRE inspired Brock Coupe.

Thanks again guys

[rcweingart]

The Roush engines are specifically built for the SPF coupe with little, if anything, having to be done to them. That doesn't matter all that much if Dennis Olthoff is doing the install as Dennis is just so experienced with the car. If Dennis is not going to do the install, I recomend that you at least buy his coupe install kit. It isn't cheap but you get all of the nuts and bolts and small things that are needed together with some proprietary things that you won't have to "reinvent the wheel" for and you can ask for Dennis' help. I don't know Eric but you got Woodsy's comment about him and I trust Woodsy - as well as Dennis - so . . . Hope that helps.