smg944

iTrader: (34)

^ thats a good write up there with alot of in depth calculations. but there is always 1 true and thats putting it down on the street. 1/4mile trap speed will always give you an accurate idea of the power you make. the are tons of calculators out there and they work out well. a dyno will always be a tuning tool. i have seen some dynos 100whp over what they should be and i have seen some under. even with good or bad starts at a drag strip you will be within 2 mph at the end of the 1/4 mile and it gives you a good basis of a whp number. i live in an area where the dynos seem to be calibrated a bit low. so here is my dyno number vs. a good online calculator.

525whp dynojet here in MA
588whp online calculator

http://www.ajdesigner.com/fl_horsepo...trap_speed.php

silverfdturbo6port

iTrader: (26)

Other factors go into a run down the track. Like full throttle shifting, Gearing and tire size and how and where they put you in the powerband. There are lots of setups out there that make numbers but dont ahve a goood powerband thru the rpm's.
If you launch shitty and loose 10-50ft of say lag or tire spin then your going to loose more than 2-3mph as your loosing track that can be used for acelleration.

Its science and math that proves that to be true.

Liborek

I agree that ploting conservative numbers into the turbo calculator is good way to separate facts from fiction but still, there are several things to consider.

Basically any posted dyno chart, to have any credibility, would have to have barometric pressure, ambient temperature, intake air temperature, humidity etc.

If the dyno isn't located at sea level and temperature and humidity are higher then standardized conditions, it will lead to lower air density. So actual uncorrected numbers would be lower than corrected. Problem is that this applies mainly to naturally aspirated engines. Turbocharged engine creates its own atmosphere, so it isn't affected that much unless compressor is operating at choke. Lower air density is compensated by higher pressure ratio. Now you apply that beloved correction factor and dyno shows even higher value then it would actualy produce at STP conditions at given manifold absolute pressure.

And also, when you realize, that dynapack doesn't have any losses from tire contact and deformation and run is done in 4th gear(direct drive), drivetrain loss must be very small and it gets lower with higher power.

Taking it all into account, I would take these numbers as crack HP figures. But thats just my opinion

But it doesn't take anything from this achievement. It's very nice combination of parts and tuning.

To the OP, you could just turn up base pressure even more. 90 psi base should be enough to max out turbocharger while keeping 0.75 Lambda and injector duty under 90%. Two 044's in parallel should have no problem to feed it even with over 120 psi discharge pressure.

It would be interesting what it could make at more boost

PDF

Those numbers appear to line up quite well. The calculator is estimating flywheel hp, where as the dyno is reading wheel hp. 588fwhp - 12% driveline loss = 517whp. Did you enter 2750lb for weight?

smg944

iTrader: (34)

if you were to be half throttle then yes it would change. but for the most part people are all out. so lets say you spin all of 1st and some of 2nd. you will have a bad 60' but since you were spinning you did not cover any distance yet. so the trap speeds will be close. the only factor is that it needs to be a clean run through all the gears. but spinning and all that wont effect the trap speed more then 2-3mph.

lets take my 10.6 run. my 60' was only a 1.97 and it still went 139.88. lets say i did a 1.5 60' my time would be around a 10.0 but my mph would be close to the same. its strange how it works but its about covering 1320' full throttle will give you a similar trap speed.

dynos are always all over the place. they are good to tune and thats all. i have dynoed on a aussie dyno in NY. i made 330whp then came here and made 448whp and my dynos tent to read low compared to others online.

sk8world

iTrader: (5)

I agree 100%. My best mph passes were always slower et's from one reason or another.
I do think your dyno numbers are low. I would guess closer to 575rwhp.

I like this calculator:
http://rx7.com/accel_calculator.html

sk8world

iTrader: (5)

I like a calculator that allows for auto vs. manual added in on the equation. .15 to .2 per a shift adds up in the 1/4.


Sorry back on topic..

Neutron

iTrader: (10)

I definitely plan to go to the track. Nothing tells you how much power you are making then mph through the 1/4 mile especially the mph gained from the 1/8 to the 1/4 mile. When I go I want to go and do it right. ET Streets, 300M axles, and rear end brace.

I will agree that dyno results vary from dyno to dyno. One thing that is comparable is cars on the same dyno, under almost identical conditions, and tuned by the same tuner. After we decided to stop tuning I asked what the tuner had done as far as Rx7 go to compare my results too. He pulled up a GT35R car, Q16 race gas, 28psi max but dropped at higher rpm. Car did 445whp which seems inline to everything that I have seen on the forum.

After doing my own logging at 20 psi I'm getting an average A/F of about 11.6, EGT's right at 1600 max.

Neutron

iTrader: (10)

I thought about raising the base pressure to 70 which is up from 59 currently (65 with no vacuum to the regulator). The injectors are only good for 105 psi I believe so 70 would give me a little wiggle room as I would not want to get too close to that number. Problem is I really don't really care about numbers and the car is ridiculously fast! I really don't see the point. I'm more then happy! The car is pretty much too fast for the street. Traction is not possible till over 70mph with NT05's, which aren't horrible tires.

My previous "fastest" car was an high 11 sec car all day and this feels much faster! I'm good for now.

That being said, I'm only human so I'm sure I'll want more soon

Turblown

iTrader: (12)

I used to dyno on that dyno all the time. Numbers are completely legit.

88rota

iTrader: (18)

Is Glen or azrr still building motors?

Neutron

iTrader: (10)

I honestly do not know and have never meet him. My car was a build in progress that included a motor built by him when I purchased it.

AaronJ

iTrader: (12)

Glenn went out of business temporarily but im pretty sure he is back to building engines again

Howard Coleman

iTrader: (6)

i would also like to offer congratulations on a well designed setup and thanks for sharing all the details and data. given a small amount of conjecture as to the dyno results my curiosity got the better of me and since you provided all the details i thought i would look at them from my perspective.


BTUs.

you can't get more out of fuel than the chemical power that resides within and that is often expressed as BTUs. there are 116,090 BTUs in a gallon of gasoline. all gasoline regardless of octane.

here's what it takes BTU-wise to make 500 rw SAE rotary hp.

500 X 1.92 = 960 CFM of air. / by 14.471 and you have pounds per minute 66.34. you find that metric on the X line on all compressor maps. that's air needed to make 500. if we use 11 to 1 AFR we divide 66.37 by 11 and get 6.03 pounds of gasoline. / by 6.35 to get gallons per minute of gasoline... .949 gallons per minute to make 500 hp at 11 AFR.

.949 GPM X 116,090 (BTUs per gallon) = 110,255 BTUs to make 500 rotary rwhp

let's calculate how many BTUs you were consuming:

6 1000 CC/Min injectors at 90% duty is 5400 CC/Min
remove slippage/lag... 5400 X .87 = 4698 CC/Min

call it 4700 and convert to gallons per minute... 1.241 GPM

E85 is your fuel which has a different BTU content. let's assume it is 85/15

one gallon E 85

.15 X 116,090 = 17,413
.85 X 76,330 = 64,880

total BTUs per gallon E85 = 82,293

you used 1.241 GPM X 82,290 = 102,126 BTUs

since it takes 110,255 BTUs to make 500 it looks like you were not there yet.

however, you were running either 59 or 65 base pressure (your comment on which pressure you ran is not clear to me)

since flow increase w the sq root:

59 would increase flow over 43.5 16.46%

65 would increase flow over 43.5 22.23%

102,126 BTUs X 1.1646 = 118,936

102,126 BTUs X 1.2223 = 124823


118936/110,255 = 1.0787 X 500 = 539

124,823/110,255 = 1.1321 X 500 = 566

since the above uses actual 85/15 ratios (E85) and you state that you were more like 90/10 you should deduct 2.5% for decreased BTU content so the final numbers are

526 hp at 59 psi static rail pressure

552 hp at 65 psi static rail pressure

of course there's always some wiggle in the data and assumptions but the calcs pretty much prove out you are where you think you are powerwise and support Turblown's experience.

it is also worth noting that the GT4088 has 7.26 sq inches of compressor area V the TO4Z at 7.0 so i am dubious that it will move significantly more air than the GT4088.

again, congratulations to all who put your beast together.

howard

Neutron

iTrader: (10)

Thanks for taking the time to do this calculation Howard. It’s much appreciated!

I am at a static base fuel pressure of 65 psi. Pretty unbelievable how close the calculation based on the data is to the dyno figures.