How much power!?

[jay]

got too say that that is an awesome power figure Joel.Well done to Geff and the boys. Just out of interest what are you goin for now? A porsche maybe.
  Cheers Jay...:wave

[bill shurvinton]

Originally posted by Carl
To give an idea of how readings vary we have had Gary Goodings at 461hp on the Dynohub(Hub reading)at 1.1 bar.That was  a ported engine too on a GT 42/45 turbo

well lets do the same 1st order approximation on these numbers.

461HP at 1.1 bar equates to 209HP at no boost. A hub dyno removes a key variable so you only have diff and gearbox losses. These are quite low, but lets say 5%. This gives 220HP at the flywheel. Given the flow limitations of a turbo manifold and the loss of efficient exhaust scavenging, these numbers are high, but I could \'just\' about be persuaded that they were possible. The EBP would certainly be lower on a 42 turbine side compared to the 35/40 which is a fairly tiddly turbine.

Look at it another way. UK spec FDs were supposed to be 260FWHP. 230 at the wheels at 10PSI would be believable with a following wind and a well set up dyno. 461 at the wheels at the same boost would have a NA 13B putting out the same power as a stock turbo. Its just not going to happen.

[Carl]

Originally posted by RE:Worx
sounds like we need a dyno day. That\'ll shut up any arguments because they will all be done on the same day on the same dyno.
same fiddle can be applied to the dyno for all cars so they could all be over 1000bhp
Bring it on!!!

Geff

Hi Geff!
About time you went on here for your self!
I can persuade the dyno guy to do a 1000 bhp run for you if you like.How much does it normally cost?
What boost would that be at?LOL

:rollin :rollin

Dyno graph would be nice to see  though too,with boost curve.

On a more serious note though I think this coming Friday the 13th should be good!I hear that the Pod may see it\'s first road going RX7 put in a 10 second run with the aid of a few upgrades,like Nos!
Wish you and Tim all the best on your attempts.Get Joel to do some runs too!
Kind regards
Carl

[bnaellis]

Would be nice to see the first rx7 do sub 12 on normal street legal tyres too.  A rx7 doing sub 11 secs on street tyres would be awesome.

[antnicuk]

Bill,

Your calculations just seem to be based on boost?  wouldnt air temp, degree of timing, fuel type/octane, all make a difference? rather than just deducting the amount of boost and coming up with a figure.  If you force 1.1 bar of hot air into an engine you would need less advance.   Only running 10 psi would mean the turbo is probably in its efficiency range, the air a LOT cooler and more advance could be run. Hence more power.  Also, Joel might have a much better I/C and the fan at the R/road might be much more powerfull,  all these would mean more power.   Gurge\'s (GSB) car is running 340 odd BHP at 7 psi, 0.5 bar.  At 0.8 he wouldnt be far off 417 bhp.  

Also, if i remember correctly, Gary had a different gear box, this could use more power to turn the wheels.  Joels gear box might be low mileage and in good nic, thus using less power.  I dont think its a simple as just deducting boost and getting a N/A BHP figure,  but then i\'m no expert, these are just my thoughts.

[bnaellis]

Originally posted by antnicuk
Bill,

Your calculations just seem to be based on boost?  wouldnt air temp, degree of timing, fuel type/octane, all make a difference? rather than just deducting the amount of boost and coming up with a figure.  If you force 1.1 bar of hot air into an engine you would need less advance.   Only running 10 psi would mean the turbo is probably in its efficiency range, the air a LOT cooler and more advance could be run. Hence more power.  Also, Joel might have a much better I/C and the fan at the R/road might be much more powerfull,  all these would mean more power.   Gurge\'s (GSB) car is running 340 odd BHP at 7 psi, 0.5 bar.  At 0.8 he wouldnt be far off 417 bhp.  

Also, if i remember correctly, Gary had a different gear box, this could use more power to turn the wheels.  Joels gear box might be low mileage and in good nic, thus using less power.  I dont think its a simple as just deducting boost and getting a N/A BHP figure,  but then i\'m no expert, these are just my thoughts.

Hi Ant,

Gurj\'s car is 347 at the flywheel though not rear wheel. So quite different from Joel\'s car. It seems a bit high for the boost but not unbelievable Royston had 348rwhp at 5800 rpm with a slipping clutch on a gt3540 at 13 psi so seems like his would of been roughly the same as Joels.

[20B_boy]

Originally posted by Carl
I hear that the Pod may see it\'s first road going RX7 put in a 10 second run with the aid of a few upgrades,like Nos!
Is Tim hooking his NOS bottle back up then?

Wish you and Tim all the best on your attempts.Get Joel to do some runs too!
Joel\'s car is sold - he wants a pickup truck!

[bill shurvinton]

Originally posted by antnicuk
Bill,

Your calculations just seem to be based on boost?  wouldnt air temp, degree of timing, fuel type/octane, all make a difference? rather than just deducting the amount of boost and coming up with a figure.  If you force 1.1 bar of hot air into an engine you would need less advance.   Only running 10 psi would mean the turbo is probably in its efficiency range, the air a LOT cooler and more advance could be run. Hence more power.  Also, Joel might have a much better I/C and the fan at the R/road might be much more powerfull,  all these would mean more power.   Gurge\'s (GSB) car is running 340 odd BHP at 7 psi, 0.5 bar.  At 0.8 he wouldnt be far off 417 bhp.  

Also, if i remember correctly, Gary had a different gear box, this could use more power to turn the wheels.  Joels gear box might be low mileage and in good nic, thus using less power.  I dont think its a simple as just deducting boost and getting a N/A BHP figure,  but then i\'m no expert, these are just my thoughts.

What I was quoting was a simple first order approximation, which is a useful engineering sense check. For a more accurate calculation you would need to take into account inlet temperatures and the reduction in density due to adiabatic heating within the compressor. Note that this would actually make the required zero boost HP HIGHER not lower.

The first order calculation assumed isothermal compression, so the boost was simply a torque multiplication off the normally aspirated figures. In other words a perfect turbo at 1 bar of boost will double the power of an engine compared to the no boost case. In this case it was enough to see that 417HP at 0.8 bar breaks fundamental laws of thermodynamics.

Rolling roads are tricky beasts. If a coastdown  is not performed as part of the power run to give a corrected flywheel estimation, then the best you can hope for is that the curve shows you the best shift points.

[Carl]

Hi Rich,
I beleive that Tim has done a little on his car to improve it bit,but not Nos at the moment.
I also beleive that Geff has had his old turbo rebuilt and is now going to try Nos too.(Don\'t play games Rich)
Of course that may not be true but you would know more than anyone except Geff if that is the case.
Either way a 10 second run at last would be very good from either of them.
Bring it onas Geff would say!
Kind regards
Carl

[20B_boy]

Originally posted by Carl
I believe that Tim has done a little on his car to improve it bit, but not Nos at the moment.
I think you\'re right, he suggested he would be fiddling in the mean time. I think he will be very close this time

I also believe that Geff has had his old turbo rebuilt and is now going to try Nos too.(Don\'t play games Rich)
I think we all like to play games Carl - thats half the fun isnt it? Yep, old turbo rebuilt - I think the installation has changed some what though... He does have a NOS kit, but I dont think that will be used next time out, a couple of other things to try first and not enough time to get it hooked up in time I dont think

Of course that may not be true but...
...it keeps people interested which cant be a bad thing.

Either way a 10 second run at last would be very good from either of them.
Totally agree, lets hope some one cracks it - I imagine Ross will have a few new tricks up his sleeve upon his return from the land of the rising sun....

Are you going up at all? How\'s Garys getting on - I heard it was getting close now? I believe he has a trick crank of some sort - looking for some high rpm\'s eh? thats one thing geffs car lacks - the power high up the rpm range is very strong but you have to shift whilst your in the midst of it. Is Garys turbo a 42/45 or a /51 do you know out of interest? some of those babies look BIG!

See u soon,

[gsb876]

Hello arguementative types:rollin :rollin :rollin ,

My car made 342bhp @ flywheel running 0.6bar boost on low boost setting as i had a leaking rad, now sorted with a new massive rad, also next week will be implementing larger injectors and a remap and possible air induction upgrade.

Will then a week later have it dyno\'d @ Thor engineering on the hubs not rolling road so should be more accurate, hopefully should be able to run @ 1.2bar???

Will post results when i get them a T78 should be good for over 500bhp, so we\'ll see what we\'ve got???

Gurj

[bill shurvinton]

That\'s in the same ball park as Gary\'s car, and again in the realms of \'possible\'. The isothermal envelope calculation puts this at 385 Flywheel at 0.8 bar. (Gary would be 380 at the same boost for the same assumptions)

So I have to conclude that with a street port you will be hard pushed to reach 400HP at the flywheel at 10PSI. So the car in question, whilst very possibly in the high 300\'s is not a 500HP car. I\'m sure with more boost it could be, but if it is/was being sold as having 500, then this incorrect.

[rx7veilside]

just to update everybody i now own joels car and the rolling road figure was wrong due to various reasons car will be back to rolling road in the near future with new exhaust the present one came from concorde i suspect.once boost is adjusted i fully expect the car to produce in the region of 440-450fwhp and 360rwhp and will be happy to post any details requested.i will say even at 0.8 bar the car goes like a train and holds the boost all the way so at 1 bar shd be very impressive.i have replied to this to put record straight and am not claiming big hp figures to impress anyone only what i realistically expect from the engine.iam not a track junkie so wont be trying to prove its figures at all just intend to have a very fast road car

[Carl]

Hi Paul,
Thanks for setting the record straight on that.
I reckon you will certainly have a beast to be very proud when the final tuning is done.The car looks excellent and appears to have all of the right mods done to it.
Kind regards
Carl

[bill shurvinton]

Well thank you on bahalf of the laws of thermodynamics for clearing that up :-)

Are you able to share any information on why the reported figures were so badly out? As well as from interests sake there was little attempt to post a correction from people with a vested interest in this engine and its power output ( not yourself I hasten to add). In fact effectively there was a defense of the incorrect figures from those who ought to know better.

Had I not pulled people up on this I am sure that there would be forum members right now thinking that you could get impossible power numbers from an engine built by a certain company.