so i was talking with chris ott (of rotary performance) today about single turbos......and he said wait a minute, grabbed some keys to one of their shop cars and says lets go for a ride, this particular car has a t-78 and a haltech with all the other goodies.....there wasn't any real noticble lag unless you are in the wrong gear, and it just keeps on pulling.....he says it has to do alot with the tuning, which he just recently finished tuning it to 19 psi and it's putting out 450 to the wheels on airplane gas.......now, this thing was hitting full boost by about 4100-4200 rpms......he says the gt 35/40 cannot compare to the t-78 at all.....i think i'm sold on the t-78...cha ching.....i guess it's kinda cool to be so close to r.p.....anyone else have any input???

 

I have the T-78 on my car and love it, but there is some lag. Full boost by 4100rpm is laggy compared to the GT35/40 which gets full boost in the low 3000rpm range. I would suspect chris has never been in a car with the GT35/40 if he is saying it doesnt compare.
My opinion is if they are getting 450 RWHP at 19lbs of boost they need to tune the car a little more

Jason

 

he said he took one (gt35/40) off the dyno just a couple of days ago...also the car we rode in had been built a few years back...chis said the street port wasn't very efficent......but this car was a no frills build.....nothing very extravagant i/e, the rp fuel pump, 550/1600, apexi front mount...etc. etc..

 

Thats cool.
I do love the T-78 and no regrets going with it. You would be happy with either turbo.

Jason

 

I hope I will be. I need to get it tuned though. Anyone? Who wants to do it? I need a good tuning at 15psi and at 22psi once I get my 3bar MAP sensor. Has Kyle tuned his GT35/40 at high boost yet? When are you supposed to get your motor back Jason? Bryan is hoping to finish mine this week, that would be great.

Scott

 

That sounds sweet

I personaly do not understand why you would want full boost @ < 3500rpm when the engine can rev to 8000rpm ? Just learn to use the gearbox and you will be OK : )

Every gear change you make even from 1st to 2nd keep you well above 4500rpm.

I do not have either of the turbo mentioned, so will not comment on the benifits or negatives of either. But it would be interesting to see someone run a back pressure test on the hybrid GT3540, V's the T78....If the GT3540 has a big negative effect (high ratio of BP to IP) then this surley will be bad for the engine/tubine in the long term when run @ the 450+rwhp level ?

 

Lag is a personal thing.

My version of lag is boost @ > 5000rpm

 

There is no such thing as lag if you know how to drive.

 

Lag is so overrated.

who drives around on a race track under 4k anyways!?

christ, shift.

 

Lag is what kills the T78 guys when we are cruising down the highway at 60Mph, drop to third, then punch it... I immediately put that T78 car at my rear bumper with my GT35/40...and so far have been able to keep them there...

I currently have an unfair advantage though...no large street ported T78 cars in town (yet). Once there is, I'll have my work cut out for me...

K

 

when are you coming to NJ ?? i just happen to have a very large street port and a T78

 

drove my car in the highway today and 60 mph at 3rd gear registers at 4600-4800 rpm, that should be enough for the T78 to pull full boost instantly.

Do you have a scan of your dyno pull with the GT3540, nocab72 ? I'd like to compare spool time with the T78.
Thx,

 

not yet on my new motor, but I have lots and lots of datalogs from pulls on the street that can be used to graph the boost curve.

K

 

next time i go drag racing. i'll datalog an entire run. that should be interesting. you will see the burnout. 20+ seconds at 8000 rpm

 

It is bad when Rice is involved with incorrect information.

Maybe his memory lapsed for a second.

Question to all:

What is the difference between lag and boost threshold?

Is appears that know one her knows the answer (other than myself).

 

You got me...

I have never heard of term "boost threshold" before...

k

 

hey jay, I do understand where you are coming from, it's just that EVERYONE here seems to call peak boost "or lack of it at low rpm" lag !, this is not correct, I have always said this.

My turbo does not make peak boost on my logger till just under 7000rpm ! the transition from vacum to positive boost pressure at any rpm above 2000rpm is around 0.02 of a second.......In my books I have NO LAG.

I agree with you, lag is a misused word in this section.

Where you get peak boost (as recorded on a data logger v's a visual boost gauge reading) is a factor of many things ranging from turbo size to engine porting to manifold specification, @ the end of the day so long as you are happy with the performance and the car pulls hard through the spread of your gear ratios and you have MINIMUM LAG once you are in your engines USEFULL RPM RANGE then your car will be fast! It does not matter if you have full boost once you engage the starter motor if your engine is not run in that range

And yes lag is a misunderstood word.

I suppose a real good test is put your engine to 4600rpm and smash the throttle, see how fast your boost gauge responds, this is a good indicator of what "lag" your system has. Better yet if you have a data logger post some results.

 

Yes, that is EXACTLY what I call lag. The time between when you MASH your foot down (within usable RPM range (4500rpm+)) and when you see a usable amount of boost.

I don't call .01 bar of boost usable, so I don't care how long it takes the needle to get to 0 from vacuum, more along the lines of going from -10 vacuum (typical cruise vacuum I would say?!?) to 10psi.

This lag my friends (or lack there of) is the primary reason why my GT35/40 setup pulls nearly a car on any of the T78 setups I've lined up with from a roll and done the 60Mph MASH.

My game now is keeping that lead...

K

PS I still don't know WTF "boost threshold" is...

 

RICE RACING already summed it up...

 

In a few weeks you will scambling for a new turbo setup.

 

I knew Rice would come back with an intelligent response

Rice explained it so it is easy to understand. Just trying to get people on here to use the proper terminology when posting. To much incorrect info flies around.

 

Doubt it.

If you tune it, you're slow.
If I tune it, I'll make sure you're slow.
If Tony tunes it, it'll likely blow up. *ouch* Sorry tony, couldn't resist...lol

All kidding aside, I think Tony and I are preparing for a "tune-off" - Vila's car with Tony's tuning, v/s Zavier's car with Kyle's tuning... (both stock blocks, both T78 cars)

K

 

To the guys who always respond with "Learn how to drive" and "shift" or "you're in the wrong gear if you have lag", what about on a tight autocross course? I'd rather be able to run my car from 3500 - 8000 RPM on the short straights and concentrate on hitting the next corner just right instead of shifting twenty times on the course.

 

Try to feed in power @ full boost happening around 3500rpm out of a tight or medium speed corner, it is near undrivable, I know That is what a hybrid turbo is like, power is consintrated in the wron rpm range, by the time you feed in the power out from the apex and start to straighten up you are up around over 4.8k (unless you dont know how to shift!) then you are ready to deliver the full power of the engine, even if you change at 8k, you are above 5k for every shift except 1st to 2nd.

My turbo set for 5k to 8.5k is much more drivable out of low speed corners than the "handgrenade style delivery of the smaller exhaust housing turbos" Friction circles of tires proclude you from using full power while cornering @ high loads so I am missing your point ? You must have an amasing amount of traction in your car ?

 

i'd have to agree... TC, or otherwise... serious electronics in order to use full power coming out of the apex.. no way that one can possibly possess that much traction in order to harness that sort of power.