At the same boost, a turbo will make more hp. As far as comparing track times for cars with = power, the difference isn't large if they are set up properly. With properly selected gears or converter, both a turbo and a blower car will be pretty darn near their max all the way down the track. The "area under the curve" concept has more applicability to street cars, provided you can get them to hook!

Rich

 

Be careful not to mixup lag, spool, and threshold. I think some people dont understand the differences between them. The size of the turbo and it's output have only so much effect. A huge turbo when sized properly will hit boost nearly the same time as a small turbo, provided you WANT it to spool then. That is a mistake many people make. The only difference in that situation is the physical mass of the shaft and blades, which can be accounted for in that many larger turbos use ball bearings.

The point on efficiency is very true. Psi isnt Psi isnt Psi (this was discussed in the forums some time ago). CFM and the Efficiency and what the Cylinder actually sees are the kings of the day. For example, a supercharger may read 12psi at the manifold on a 218/218 116LSA cam, but swap the same duration for a 110LSA. You can bet in lower rpm you will have a very different power curve. Psi is the same, but that really only means so much.

With a turbo you have two thoughts, midrange or peak. Supras either are high peak cars or good midrange cars. It depends on what the car is good for. Peak cars work fine on the strip (Aside from 1st gear if that even is an issue, as long as you can hook, just launch it higher in the rev range)... However on the street the wider tq curve is king, again, provided you can hook 12psi in 1st gear at 30mph. Can you? Doubt it. The power is a waste in that case.

I also have a turbo cam that looks more like a supercharger cam. The pattern of what works best is wide and openly opinionated. The comment of "because of the cam VS despite the cam" is very true. If the cam matches the heads very well, and the turbine was set to match the cam/heads very well, then there should be no major difference. Minor, perhaps, but by then you could say that the temperature of the ambient air on that day made a big difference too. Tiny variables worth 5-10hp here or there, or even more. They can be controlled to a degree.

The results from the roots/centrifugal/turbo were right on, but they didnt want to step on any toes and say which was best. Their points were great and very well thought... The hp/tq numbers all vary - but the final HP numbers are very close. That is proper. It SHOULD be that way.

It all really comes down to what you want the car for. Roots make boost like a turbo and have less peak then the rest. Turbos make boost fast and when sized right hold it well, and have a nice peak. Superchargers usually have a better peak, but less midrange. Thats all their is to it. What do you want from your car?

I think though the turbo will generate approx 12rwhp more peak, but it will generate nearly 20lbft of tq more at tq peak.

 

For the record, my guess is that it makes 10 less peak hp with the turbo, but 100 more ft-lb torque.

 

it has nothing to do with what results i "want".....i have no concern over which wins because im running nitrous!
it just seems to me this really isnt an optimal comparison of the two, so you cant really declare which one is "better".
i didnt meant anything personal so please do not take it that way.



i did more reading and found i was wrong about that, its done to stop exhaust gas reversion, which robs power.


i said high power cars, not stock cam or basic upgrades.

look at the 9-10 second cars if they list their cam.......5 ar on the turbobuick.com main page, and only 3 list their cam profile........all 3 are equal duration cams.
10s, solid roller 224/224
9.601 , solid roller 248/248
9.89 , flat tappet hyd cam 218/218

i did check out a few GN performance websites and could not find any listing a performance cam with a greater exhaust duration. heres is one shops list
206/206
208/208
212/212
218/212
224/224



LSA could have played a big difference.

and btw, i wasnt stating that you couldnt make huge power with a larger exhaust duration..........i simply said that the majority of turbo cams i have seen for high hp cars dont have them.


now youre just being rediculous. i never said it "wont work"


very true............but the turbo buick guys have been playing with turbo cams for quite awhile now, and im pretty sure they wouldnt be using something that holds them back.


i did not say there was anything wrong with the quality of your kit.

i simply said that a log-style manifold is the least optimal for a turbo.
a tubular header-style manifold will flow better and make more power.
that is a well accepted fact.

BTW, the stock manifolds are closer to a header design, not a log.
W2W's car made 1329hp and 1138tq with stock iron truck manifolds.
FYI, their cam duration for that car is 242/238.


once again, i didnt mean anyting personally, ive read many of your posts on this board for a long time and you always had a lot of good info.

i also have nothing against the test you are conducting, i find stuff like this fun and interesting to see results, just like everyone else.

i was just pointing out that the test is less than optimal for the turbo, so it really shouldnt be used as a basis to judge whether a turbo or supercharger is "better".

 

Jose seems pretty knowledgable about turbos.........this is what he has on his site.


Duration when using a manifold or log design on most turbo cams is usually about 6 degrees more intake duration than exhaust duration (226/220, 240/234). This is mainly because a manifold/log design will typically see higher then a 2:1 pressure ratio in the exhaust ( as high as 4:1 with some logs). By using a reverse split duration this will somewhat help prevent from getting exhaust gas reversion.

Duration when using an efficient header setup with most turbo cams will usually be (230/230, 224/224) or better known as a dual pattern cam. The thinking is with the exhaust backpressure being only 2:1 you can leave the exhaust valve open a little longer then if the exhaust backpressure was 3:1 or higher. Also some of the new turbo designs produce a much lower backpressure with the advent of better flowing turbine wheels and housings which further decrease the total amount of backpressure created by the system


we all know harlan is doing great with his turbo setup, heres his advice

My personal thing with it is, get all the intake charge in the motor you can w/ the longer intake duration and keep the exhaust shorter to keep the exhaust energy up. Since you're fighting a large backpressure on the hot side it makes sense to me to keep the valve open time to a minimum and get it out quick.

hes using a 251/248

 

Keep us posted Mike.

What is that turbo capable of power-wise?

My only concern is that the T-Trim is rated for up to 825crank hp and the T76's I have heard can go over 1100 crank hp?

I agree with you about the cam selection, it's not going to kill the combo IMO.

Where did your old combo peak HP and TQ?

 

There have been claims of turbo buicks that have run 10s on the stock cam. Just go over to turbobuick.com and ask about a cam choice to run low 11s. I guarantee someone will chime in a say that a stock cam has run into the 10s.

Those are the most common cams people put in the LC2 motor. The one common cam you did miss is a split duration, 204/214 (or 210/214), either way there's more duration on the exhaust. Oh, a guy in Newport News, Va had that split duration cam in his car and went 10s.

Later.

 

I am guessing you will be within 5hp (either one could be higher), but the turbo will make 40rwtq more.

 

I'd like to see an overlay of the dyno graphs.

 

That would be sweet

 

dang man...thats awesome your testing this out. Let me know how it goes. I'm very interested in the results.

Oh..we need to get together on that crank some time.

 

Make sure you are using a T76 of equal capability. If your using a 76GTS, then its in favor of the turbo by a good deal. A standard T76 Q-trim is your best bet.

 

Dang! Well let me send this GTS back and order up a GTQ. . .

Actually, the T-76 compressor is roughly the same dimensions as a T-trim, if not smaller. If the 76 GTS has a more efficient exhaust housing (drive mechanism), then it should get credit (hp) for it.

Mike

 

Impeller size though they are similar only tells half the battle. Yes drive mechanism makes a difference as well. But the most important thing people forget is impeller rpm. A T-trim max impeller speed is 55000. A T76, well it will be well over 90000 rpms.

 

just a guess but i'll say 7 more rwhp and 65 rwtq

good luck