Chronos

Sometimes I think we bank too much on maximum hp numbers rather than the overall power curve...Looking at this graph I got off Wargasm's site (or whoever hosts that dyno results site) it really illustrates how a strong power curve will give you greater acceleration through the gears.

Another thing is I can't beleive how the T-78 spooled up quicker and the GT35/40 had the higher power at the top-end. I suppose it could be that these two are set up a lot different, but isn't it supposed to be the other way around??? The GT35/40 is BB afterall where the T-78 is not.

fastrotaries

i always thought that you should be more concerned with the overall TQ curve.

Chronos

Torque?

twokrx7

iTrader: (1)

The hp or torque curve at the top end can be effected by boost control amongt many others. It is common for a single turbo with external wg to suffer from a drop in boost toward redline, especially if operating much above spring pressure or with high backpressure. Tuning also has a bit to do with it, seen many dynos on the Forum with AFR all over the map from rich to lean. We rarely know what timing is being used or what ve the motor has given porting, manifolds, etc.

Tough to compare two seperate cars with different turbo kits unless you know the cars and owners well.

Even some boost gages are off by a psi or two ...

Chronos

Yeah, that's what I figured in regards to these two cars...but which car do you think is faster? It looks to me like the T78 car is at a higher power level for a longer amount of time thus giving it better acceleration and overall power. Just weird for a 430hp car to beat a 470hp car with exactly the same chasis, transmission, gearing, etc.

Jason

iTrader: (5)

There are too many factors when comparing those dynos. A couple are how much boost were they running and what is the AFR ratio of each setup. A properly tuned T-78 is going to put down more than a GT35/40 at the same boost levels.

Jason

RICE RACING

EASILY !

A gt35/40 realy is a power challenged unit compared to MANY other turbos, it provides excellent responce and low rev power, good for up to 500rwhp when pushed but after that it's VERY FEW and far between who is making more than that number on moderate boost levels.

And I don't give a rats *** about how much "average" power you think you might have. Get a plot from 5.5k to 8.8k rpm put this in a good data analysis program and see what will be faster !

A 600+rwhp T78 car will kill a gt35/40 machine everytime, people talk about "average power" under a curve but they neglect to see how much time an engine spends in a certain power range when it's accelerating through this "curve" to it's maximum red line

Go get cartest2000, play with the "curves" and you will soon see the light, science and mathematics don't lie only people with "ego's" & "opinions" do

Poweraxel

why are we even comparing the GT35/40 and the T-78.. these are 2 totally different sized turbos...The T-78 is a much larger mitsu turbo .... that turbo is actually too big for most owners out there... this is like comparing apples and pineapples

Chronos

Heh, Speaking of Pineapples, As we speak I'm having a 5 year motor built with 2piece 3mm ceramic seals and a Large street port at Pineapple racing. With the ceramic seals (less heavy and let you use stronger spring pressure to resist floating) and that level of porting, what kind of rev's do you guys think I could run at a safe level?

My car will be a weekend street car as well as a part time track car and I feel the GT35/40's fast spooling and smaller size would yeild the best results by far for street driving and autocross but still be very capable on the road track...The T-78 on the other hand would have too much turbo lag for street driving and autocross but if kept above 4k rpm, might prove to be the best unit for road racing - especially if I increase my Rev Limiter so I upshift into a higher RPM. What do you guys think???


Ohh yeah, and does anyone have the installation files for that cartest2000 program? Sounds like an awesome tool!

twokrx7

iTrader: (1)

T78 is not laggy, have you ever driven a single turbo car that hits 15+psi at 4k rpm? What you have is a fast car that simply requires the driver to use the car where the power is. Lag is only an issue if you loaf the motor below 3k rpm but want to have instant throttle response.

I personally think the T78 is one of the better sized turbos for a street third gen. Decent spool with capability to turn up the boost to 20+ without restricting the hot side of the motor too much. Seems to hold up well to both street and track use, nice piece for an oil cooled center.

Wargasm

A lot of what makes a turbo "right" for one person but "wrong" for another is how they drive. How they REALLY drive, not how they THINK they drive.

For example... Many people would say that my daily driver Acura RSX-S has no power down low. Well sure, the power doesn't really start coming on until 5500-6000 RPM, but I do not drive it much below that almost ever. I am completely serious. A very typical cruising RPM for me in that car might be 5000. I'll sit there and run it at 5000 for 30 minutes straight just cruising along on the highway. That way when I want to go faster I just mash the gas. That car sees WOT a LOT hahaha.

So getting back to turbos... Most people (including me) say that a T78 is a little laggy for most people and that a T04S or a GT35/40 or something even smaller would be a better pick. The reason I say this is because most people THINK they are speed racer types and will be able to keep a T78 happy up at 6000-8500 RPM all day long. In reality, most people are going to poke around at 2500 RPM and then try to step on the gas to race someone. They will not be satisfied with the way the car works with their driving habits.

I drive my RX-7 around at about 3500-4000 RPM cruising speed. This fits VERY well with my T04S turbo. If I hit the gas from there I pretty much have instant power and a lot of it. I run 14 PSI and I can have full boost by around 3500-4000 RPM. That turbo on my car works for me and the way I drive. Some people have the Apex RX-6 or T04E and LOVE THEM. For me I'm sure they would be too small.

A note on dynos... I find that looking at one dyno for each turbo doesn't tell the whole story. I try to find as many dynos for each turbo as possible and get a feeling for trends. Tuning plays a large part in any highly modded single turbo car, so you want to try to find as many datapoints as possible so you can form an educated opinion about them.

Just my $0.02

Brian

Chronos

Haha, good point Brian. I was looking for people's opinions on how each turbo would perform on the track which typically means 4,000rpm and above and taking into consideration the increased redline possible with the porting and harder spring pressure from the ceramic seals.

By the way, I like the way you drive! Go ahead and post some stories with your Acura on my daily beater thread! https://www.rx7club.com/forum/showth...hreadid=202700

Marshall

You want a real shocker, compare Boostn7s non seq 18psi run to a lot of singles.

Carlos Iglesias

iTrader: (6)

I've done 19 psi on non-seqs, and yes the stocker can put out some power. BUT, you might as well count down EACH AND EVERY TIME you do that because at those turbosshaft speeds, bearing life is a miniscule fraction of the speeds at stock boost OR singles overall. You might as well change your oil filter also while your at it because there IS turbo bearing material in it. I've seen it firsthand in Cam race car when he asked me to help crew for him at Daytona about 6 years ago. BTW, he was only running 15 psi in qualifying.

As for the original discussion, my understanding of what matters with regard to acceleration is area under the curve (i.e integration of the HP curve) between the applicable high and low rpm points. For most race conditions, these points for "useful" powerband are defined by the shift point at the top and the the lowest resulting"post-shift" rpm point. Of course this doesn't take into account driver inefficiency if the initial power application commences outside of the powerband (i.e less that the lowest "post-shift" rpm.)

45psi

Was this done on the same car. What about the AR. for the gt35/40.

infinitebass

I thought that the gt35/40 will hit 15psi around 3200-3500 rpm's...

Blake

Chronos

This was done on two different cars.

Carl Byck

Who's 3540 dyno is that? I could not find it on the site. Carl

Chronos

Sorry, I saved the graph a long time ago in excel format, I thought I got it off of wargasm's site but I might have found it somewhere else.