-stig-

hello guys!

just a quick question!

I made 529rwhp on my bridge ported t-78 powered 13b rew..

everything on the engine supports more, the thing that stopped my last time was the exhaust just being 3", now its 4"!

but to the question, do anyone know how far the t-78 goes when it comes to rwhp on rotaty engines? how much it can flow?

i think the turbo is a 33D, but not shure.. i did'nt buy a kit, just the turbo, and its not marked!

just wondered if i had to change turbo...

Stig

Howard Coleman

iTrader: (6)

T-78

66 X 90 7.584 sq inches of compressor

65 X 74 5.903 sq inches of turbine (P trim or thereabouts)

hotside is only 77.8% of compressor which should create a fair amount of backpressure.

next turbo down from T78 is GT4088 at 7.26 compr 6.633 hotside and flows 72 pounds at 26 psi. your turbo should flow a touch more but there is no compressor map.

given you made 529... that requires 1015 CFM or 70 pounds per minute. what method of correction did the dyno operator use?

turbos up from yours:

T88 same comp, larger hot

T66 7.657 and 5.8944

BW S300sx3 7.743 7.151 80 pounds

BW S366 7.743 7.151

GT4094r 8.175 X 6.423

hc

Yukitama

If your turbo is what you think it is, theoretically you are only 1 hp away from the maximum it will do on a rotary.

-stig-

the correction was DIN, on a Dynapack.

humm, if i dont got any more to give with this, even with bigger exhaust i think a change is comming! would it be empty on just 24psi?

i like the spool on this old bastard, but just dynoed a couple of gt4088 and gt4084r and they where pretty close on the spool! so if a gt4094r flows a bit more, it would be a good choise!

regards.

-stig-

here's the chart.

can it be a bigger t78? has greddy delivered one that flowed more? or have i just maxed it?

was done with pump fuel, and 700cc 50/50 water/meth. 24psi boost..

R-R-Rx7

iTrader: (24)

you can machine the compressor housing and fit a t88 wheel if you wanna use the same turbo

-stig-

but if i fit a bigger compressor wheel on the t-78, wouldnt the difference between comp/exhaust be even bigger, and then more backpressure?

Howard Coleman

iTrader: (6)

as we know, it is hp under the curve that wins races. in other words, it isn't all about the top tick number if you are looking to win something other than points on a forum.

there really is alot of helpful clues available from your dyno chart.

to get a sense of midrange i note the rpm at which the motor makes 200 SAE rwhp. it is generally between 4000 and 5000.

i also look at 5500 to see what the hp level is. a properly fixtured 2 rotor should make 400 SAE rwhp at 5500.

obviously, you really don't use these lower rpms while racing (although you do touch 5500 going from 1st to second, second to 3rd and you hit the later gears at 5600 so you are close...) but these lower rpms are an indication of forward spool.

i only work in SAE corrected hp. your correction adds approx 10 hp to your numbers. your turbo is making 200 SAE at 5000. that is on the end of the wrong end of the spool range.

further, you are making only 335 SAE at 5500.

so your midrange could use some help.

given how power levels out it appears that your boostcontrol opens at 5800. things stop increasing at that point. you have a large compressor, larger than the typical 67 mm, so you
should be able to make more than 550 SAE which is 564 DIN.

your compressor is 7.584 V 7.07 for a 67 mm. (TO4z etc).

w it's advantageous 55 trim it should spool even w the smaller overall TO4z wheel since it has a slow spooling 63 trim.

many items effect midrange hp. timing and exhaust ports top my list, other items are manifolding both before and after the engine including airfilter restriction.

given your dyno sheet i would say there are many things to work before giving up on the turbo. BTW, the T88 is not significant as a size upgrade.


howard

Turblown

iTrader: (12)

Have you done a compression check lately? Turbo looks awfully laggy, that or it is a T88-33D. If you've ever seen one in person apart you would know why they are slow to spool...

-stig-

this engine is the first one i build, so it has a couple of things i'm not happy with, a bit big clearances and so on. i have not taken a compressiontest in a long time, it starts easy to be a fully bridge, ( secondary size ports and bridges on all 4 ports).

Hell of alot nice info there Howard! looks like i should throw the engine out and take a look at it! i know the exhaust ports isnt as good as they could be, given the eally big intake ports..

i dont know how the ignition advance affects the spool, but took a screenshot of my ignition and post it! i think its a bit low under the spool, but i have not tried any more advanced than this yet...

stig

-stig-

and the turbo is stamped greddy t78, but thats all i know... can take some measurements when i come home from work here at sea.

Turblown

iTrader: (12)

Low boost areas under 5.5k could use several more degrees advance, unless you are running very lean there. It depends on what your EGTs are.

-stig-

EGT's are pretty low, was climbing at the top, but thats probably due to the 3" exhaust.

not so in to the rotary ignition adjustments yet! using LS2 truck coils!

Howard Coleman

iTrader: (6)

"EGT's are pretty low"

egts are often only used at the top of a run. generally they do rise w output. however egts are perhaps more helpful in the zero to one bar area as they greatly effect spool and therefore midrange.

egts must be preturbo and be digitally logged into the cells you use for tuning.

you are looking for 1400 F from zero to one bar and even if your AFRs are spot on you will find a great deal of additional power by working w the timing in that area of the map to produce 1400.

i see alot of tuned motors at 1050-1100.

you may find retarding the timing is the right direction. i did.

i picked up alot of midrange hp and my AFRs didn't change. hotter exhaust spools the turbo harder.

-stig-

i've got the egt pre turbo, and i cant remember what it was during spoolup, but it was over 600 celsius/1100F. would'nt the afr affect the egt a bit? what afr do you shoot for in the 0-1bar zone?

i dont have the afr curve here, but i usually go from 12.5 at 0bar, and down to 11.5 at 1bar.. there the water/meth comes on.

s3tpwr

last summer my bridgeport fd T78 turbo put down 544 rwhp on a dynapak @19psi running out of fuel 850 1600cc inj combo
i then swaped the motor in d Rx-4 with a bw s475 and put down 680rwhp @ 22psi
i used Q16 fuel and LS2 coils on both set up two 1300cc and had 4 1600cc wired up but only used 2 of them
i would go with the bws475 on a bridgeport it comes on fast and pulls real hard

s3tpwr

i am pretty sure the T78 would have made another 50-80 hp easyon the bridgeport seeing these turbos like the 25-30psi range

-stig-

544 @ 19psi is just awsome!

would you share some info about the engine, setup and tuning??

smg944

iTrader: (34)

i dont think your 3" exhaust is holding you back as v8kila made 685whp with a 3" exhaust and a re-routed wastegate.

did you buy the turbo new? if not did you happen to pull of the turbine housing and check the blade? possible damage to the blade could cause issues with power on high boost and slow spool.

-stig-

685 with 3" exhaust is just impressive! thats the first over 600 i've seen on 3" rotary!

hmm, but then somthing else is stopping me, have shopped around, so now i'm going to measure pressure both pre and post turbo, see if there is some info there!

have had the turbo apart a few times, so yes its just like new! bought it rebuild!

-stig-

anyone else have something useful for me?

thanks!

-stig-

just to get back to this tread, the turbo turns out to be a t88 33d.

i took it out to rebuild it, and it looked kind of big next to a gt4088 i had on the bench, so i measured it and then found out what it really was

Cosmo_TT

iTrader: (11)

so, is that good or bad, good if you wanted more power, right?

Liborek

Did you get to measure it? T88-33d has huge hotside, so for bridgeport it should be more than adequate, but if you suspect that post-turbo pressure is high, it will show also on pre-turbine pressure and then it won´t make power.

jetlude

iTrader: (9)

Howard, what AFR do you aim for in the 0 - 1bar range?