Rear Wheel HP results

[James]

Ron, your are right about Brighton - it is weird! No 11 sec runs yet.

However, my car will be weighed - with corner weight scales very soon.

I know my engine develops 450hp - dyno tested by Knight Racing.

I know the Car Test programme is accurate.

It is giving me a figure of the mid 11's.

AND, I know that piece of road very well. I drive down it twice every single day on the way to and from work.

So I should have a good chance.

Time will tell. /ubbthreads/images/graemlins/cool.gif

Regards,

J.P

 

[Ron Earp]

Be interesting to see what the 450hp translates into on the chassis dyno. Roy's car is over 500+ rear wheel hp - still no 11s runs that I know of. I think you guys have longer quarter miles over there!

 

Ron, you have PM.

 

[Rick Merz]

Is the track level or going up hill? 500hp at the wheels should be around 11.0 to 11.5 in the 1/4 mi.

 

[James]

Its flat as the eye can see it. Being by the sea you can be lucky and get a following wind. The last few years have been very warm with little wind. Who knows this year we might have a Force 8 gale and see some 10 sec runs! /ubbthreads/images/graemlins/grin.gif

 

[John]

Is the rear suspension that bad at hooking up? Is it that the shift time is slow with the cable linkage?

I know of guys with big heavy 3500 pound Camaros and Chevelles who have relatively mild (400-450 horse) engines putting them into the mid 11 second range. Granted they've done a lot of tuning to get there... 60' times in the 1.60 second range. There is one guy I'm familiar with in New Jersey who has a 3800 pound chevelle with a very streetable 427 built for nothing but midrange torque down in the low 10s! All with pretty much factory parts and a solid lifter cam!

What kind of 60' times are we talking with the GT?

John

 

[James]

Not sure about 60' times. Most guys who compete are using solid rod change gear changes with Quaife LSD's and slicks. Paul Thomspson has posted before about gear change times, I think?

Problem with Brighton is that the surface is not very grippy, so you lose a little at the start, but then its just plain sailing! Just got my entry forms through this morning for Brighton. 11th September.

Regards,

J.P

 

[Paul Thompson 'Hooligan']

Hi all -

Thought I'd pipe up as it is Roy's car that is being referred to in a number of replies. The car was built as a lightweight GTD but we have not weighed it for sometime. We estimate it to be approx 1050kg (definately without me in it!!)
Power - who knows? - strangely enough I have always put quite a lot of credance in engine dyno results as opposed to chassis dyno results. Although I do think that trap speeds on the quarter give an indication.

Roy's car has been on a chassis dyno (Progress Engineering) once - when we were checking for flat spots and Lambda up to approx 6000rpm.

We did not get a printed output of any description, but the operators were 'impressed', to use their words. The operator indicated 'in excess of 500 at 6000rpm'.

He ignored 'flash readings' and demonstrated how a dyno operator can record high spikes if he choose's to, something he did'nt.

Progress did not build the engine so had no point to prove, they did however dynamically balance throughout after Roy had 'got it near' by welding additional material to the custom crower crank. This is also why they were interested in testing just to see if it all stayed together!!! /ubbthreads/images/graemlins/grin.gif

Re Brighton - I dunno - they don't give 64ft times there but we have recorded sub 2 seconds elsewhere (but not often!)
The norm average is nearer 2.5s. Gearchanges are slow with the Renault box, best we ever recorded was 0.3s (straight) and 0.5 (across the gate), those being on a cable change, I believe the Rod Change to be no faster, possibly a 10th slower.

At Brighton 2003, a nearby touring car team was recording windspeed etc etc and said there was an average of 8-15 mph headwind. Whilst this must have an effect, I have no idea just how much.

Roy has managed 12.03 and I 12.1 - both reaching 132 on the quarter - so it should be there, lets hope for a good 2004.

Finally - re 'our quarters being longer' than those across the pond?? - who knows? - our gallons are 20% bigger!!! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

 

[Ron Earp]

[ QUOTE ]
Thought I'd pipe up as it is Roy's car that is being referred to in a number of replies. The car was built as a lightweight GTD but we have not weighed it for sometime. We estimate it to be approx 1050kg (definately without me in it!!)

Power - who knows? - strangely enough I have always put quite a lot of credance in engine dyno results as opposed to chassis dyno results. Although I do think that trap speeds on the quarter give an indication.

[/ QUOTE ]

Hoping you'd chime in Paul, can't except Roy to get on here to often I know!!!! ;-)

I am the opposite - I like chassis dynos, particularily Dynojets since I'm familar with them and have used them for years. I've see LOTS of 500hp engines suddenly become 350hp engines on the chassis dyno, making 300 rear wheel hp.

I've been thinking like Malcolm M for awhile too - I don't buy a flat percentage loss for chassis figures. I think this was discussed sometime ago, but my question of if it is a percentage and we make 500 rear wheel hp where does the 15-20%, or 75-100hp go that is lost in the drivetrain? That was never answer. That is a lot of heat, and the transmission isn't going to dissipate that sort of heat happily.

If your car weighs in at say 1150 kg with you and lots of extra fuel, cookies, and beer, that is 2535 lbs. Using the standard calculations for hp/trap speed this would work out to about 450hp rear wheel for 132mph. So, based on your chassis dyno reults and ET it'd appear you're leaving a lot on the table, which we have all sort of figured before.

Still, 132 mph means some power is definitely there but traction and gear changes are an issue. The 60ft times stink, at over 2 secs, but those are similar to what I was turning with my Lotus. It is just hard to bang through the gears in these boxes. But 2.5s is really bad!!!! You'll need much less than 2.0s to get into the 11s by much so some work is needed on the off-line traction and launch. I think it has to do with weight transfer on the launch as the chassis isn't forgiving at all.

JP, you best practice a lot because at the "fast level", less than 12.5-13s, those programs don't have much to do with reality! Getting hp and mph is one thing, but ETs are a whole different ball game.

 

As you can imagine, I am with Ron 1000%. Chassis Dyno is REAL , IMHO. All the people I took for rides in my 40 told me it was faaaast! But, I knew it was a DOG, the chassis Dyno proved it.

If you think you have 600HP motor and the Dyno says 330. Either the Dyno is bad, or you are being wishful! Hang around the Dyno shop and watch a turbo 4 banger register 300+, then you will have a better idea.

 

[Ron Earp]

Yep, my next door neighbor (whom I like dearly if he is reading and couldn't have made a better match for a neighbor) just dropped a "400hp" SB Chevy into his new rod (he builds lots of nice ones). I'm trying to get him to come down to the dyno with it and tune it up but he is a little reluctant. My guess is that it'll be weaker than my turbo four on steriods and he doesn't want to see that happen, he's mentioned that himself! /ubbthreads/images/graemlins/smile.gif

Dynos can be calibrated and are fairly reliable, or at least I've found the one I use to be so. All that matters is what you get to the ground, not what the engine dyno says nor what your calculator indicates.

I still want to solve the mystery of the "% loss" or "flat loss" in the drivetrain.

Ron

 

[roaldin]

Ron,

Re:- "static" vs "percentage" drivetrain losses.

A reasonably well known Sydney performance identity has played around with this.
He claims that there is both a "static loss" and a "percentage loss".
Unfortunately there seem to be too many variables to come up with a rule of thumb.
If I can find his discussion I'll post it.

Tim.

 

[Howard Jones]

I was talking to my prostock friend today and I asked him about 1/4 mile times. He said in that to run 11.90 with about 400hp and 2500 pounds you will need to do 1.5 sec 60 foot times. He also told me that that thing will never transfer weight properly to drag race it. Lastly slicks properly heated up on a grippy track at worth at least 1 sec and as much as 2 if the car has wheelie bars and really hooks up, no wheel spin. By the way he was taking about launchs at about 500-1000 revs above the max torque point to start out. Just drop the clutch and floor it. Does anyone really think that these tranaxles can take that for long?

These are NOT drag race cars!

 

[James]

In the U.K we know that the Quaife modified Renault box will take the torque, I'd be more concerned with driveshafts and C.V joints breaking. That does happen, especially to Mr Leadfoot aka Dave Parker.

I'll be setting my 40 for 1/4's. I'll be changing the damper settings front and rear, and of course the tire pressures. I might even buy some drag radial tires just for the day!

I've got a data logger, and yes Ron I'll be practicing plenty!!

Regards,

J.P

 

[Malcolm]

The weather plays a big role at Brighton. This year will be my 12th run there. The prevailing wind direction is normally South East which should remove head wind but the number of occaisions at Brighton when sunshine, correct wind direction and mechanical reliability (the driver is always perfect!!!!) come together is fustratingly rare. Actually I have occaisionally missed the odd gear change in both cable and rod linkage formats.

In 1994, whilst the world windsurfing championships were happening just a bit further down the beach I had my best ever run on a "my mate built built me this engine" engine, claimed 350 flywheel bhp, laterly dynoed at 306 rear wheel bhp, using Ray Christophers rear slicks produced a 12.6 sec run. My car is not a lightwieght and I guess its weight is 1250kg.

Grip is critical and getting a sub 2 sec 64 ft time is very rare in a GTD. However I would say a 2.25 sec is reasonably acheivable for regular competitive drivers.

However my more recent theory, based upon my own experience, is on tyre diameters. The slicks used are small diameter compared to road tyres and compared to the Goodyear Bluestreaks and Dunlop Post Historic tyres. I do not consider my Dunlops a handicap on the start line but I do consider them a handicap after quarter distance ie when I am in 2nd gear and above. My drive ratios are poorer compared to the slick shod guys slowing up acceleration. This reflects in my slighty worse overall times and the slowest terminal speeds recorded in the last few years. Since I went to Dunlops I have never got into the 12s! Wendy and I will be on slicks for Brighton only this year. All being equal weather and reliability wise to last year I would place my penny bet on beating my times and speeds from last year. And I hope to see Wendy improve too.

 

[James]

Malcolm,

I think you meant that the prevailing wind was South West. I too believe that gearing is all important. The M Coupe revved all the way up to 7500RPM - I went over the line in 3rd gear.

The engine Dave Millam built me has max power at 6600RPM, so I've got high RPM on my side, I'll set my redline at 7000RPM.

I hope to improve on last year that is for sure!

Regards,

J.P

 

[Malcolm]

Correct JP, I did mean South West for the wind direction. And if you come out and do a 11.xx with your MDA, Lord help us all as we shall never hear the end of it! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

I had to shoot out before I could finish the full posting above so wanted to comment on the fixed and % loss concept of gearbox drain on bhp. This concept I can subscribe to. Within the working temperatures of the oils and bearings the loss will be a reasonably static amount, what I would class as fixed, given any engine in front of the gearbox. As rotational speeds and acceleration of parts becomes quicker through more bhp driving things around, you will get beyond the nromal operating tolerances and spec of the parts involved and then you will get a % drain on bhp to add to this fixed loss. A bit like wind. At road speeds wind resistance isn't as big a problem as at higher speeds. In my old Cobra replica at 120 mhp you hit a very big brick wall with regards to wind resistance. Betweeen 0 and 70 mph it isn't a consideration as that is nromal operating speed. Correspondingly go from 120 mph to 150 mph and the increase in drag is much more than the increase in drag for a speed range between 60 mph and 90 mph. I think the same concepts apply to power drain on gearboxes but for day to day running a fixed loss is an acceptable concept. IMHO of course!

 

[Max Walter]

[ QUOTE ]
Finally - re 'our quarters being longer' than those across the pond?? - who knows? - our gallons are 20% bigger!!! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif


[/ QUOTE ]

According to OnlineConversion.com:-
1 mile [statute, UK] = 0.999998 mile [statute, US] /ubbthreads/images/graemlins/crazy.gif

I guess that makes all the difference!! /ubbthreads/images/graemlins/wink.gif

Max

 

[Howard Jones]

Ok here's my pro stock buddies thoughts on 60 ft times. He runs his pro stock car to 60 feet in .96 sec. and leaves the line at 7000Rpms. He also said that to run high elevens with a 2500 pound car and 400 hp we will need to run 1.3- 1.4 sec 60 foot times.

His recomendations. Do all that is possible to make your car's rear suspension work like a live axle. The camber change is eating up all the grip as it goes neg. I told him that most cars have somthing like 300-400 pound springs on the rear, and he said double that at least. You will be going for keeping the rear tires as straight up and down, 0 camber angle, as possible for the 100ft or so. Also the front shocks will need to be set to the lowest rebound setting, softest rebound, and try to get the car to stay up on the compression stroke of the front shocks after they extend to at least the 100 foot mark. "You will need to leave at 5500rpm and floor it as the chutch engages. Use slicks and you will need to not get ANY wheel spin. Until you get the 60 foot times consistanty under 1.4 seconds you will be in trouble. The engine should make as much power as the traction will allow AND get the 60 ft times where they need to be"

His sons car is a 2500 pound camaro with a 750 hp big block, runs a 1.25 sec 60ft time and will go high 8s. That car does not spin the tires on launch and leaves at 6500rpm.

As you can see from above 2.5 sec 60ft times are costing us a full second. Most of this is due to the road race setup and tires. Those 12.0 cars are really 11 sec cars that can't get launched properly. But I bet they feel like a 11 sec car after thet get going.

Still want to drag race?

 

[Mark Worthington]

As I've read the last few posts I've had visions of exploding transaxles in my head.