engineermike

You're down 150-200 hp. I'd be checking things like bad muffler (open up the headers and see what happens), TB not opening all the way, (as mentioned) not running on all cylinders, and bad converter.

Texas_WS6

iTrader: (9)

I realy hope this does not come across rude. I have done all these things except the dyno, had issues with sceduling. No cats, trans is good, and built, converter slipage is less then 14%, not too bad for the 3600 TCI stall. Elevation is 3500 feet with a DA on those days of just oer 6000. That said, like I have said before, this thing is no faster then my cam only 346 that it replaced. The same day I ran the 12.77, my buddy with a SS 346 cam/heads car ran 12.30's, same converter, same trans, same rear end gearing, same tire size. He does have the MS3 cam which is a Comp Lobe grinds. Scanned the car every time and saw no knock until I got to 32 degrees total timing. Injecter duty cycle never excedded 71%. Timing steady and fuel not being pulled from it. Best run was at 12.8:1 AFR. I actually have two WB and two EGT's on the car. So I would think the chance of a WB being off is minumal due to the facgt I log both and would see a descrepincy between them, and the EGT's never get over 950 degrees threw the runs.

As far as a dyno goes, you should be able to do the same thing at a track if you know how to read your time slips, and you have a data logger. I do not mind going to the dyno, I just do not believe the dyno is any better then the track.

450 to 500, well if thats all this thing should make at the crank, then I was robbed of 12,000 dollars. I belive it is making close to 400 crank now at altitude and such a high DA, take it to sea level and it will probley make 450 to 500 crank, but I paid for 580-600 crank. Not only did my builder promise me this, other builder shops told me the combo should make that (sponsors) as well. Can they all be wrong? If not then were is the rest of the power? The only difference between the sponsor's build's and the actual builders build is the cam manufacture.

Again, it is hard to type what all I have gone threw on this without sounding rude, I do not mean to be and I am not trying to talk anyone down. I am just frusterated with the crappy performance I got for my $12,000. So if I sound rude, please forgive me.

98Z28CobraKiller

iTrader: (17)

In addition to the above, check your voltage at WOT. It shouldn't take too much to figure out where the missing 100+ rwhp is at. Does it make any noises? There are only a few things that could cause this problem.

weak ignition
excessive inj duty cycle (not enough pump)
Intake restriction
Exhaust restriction
REALLY bad valve train configuration
power loss thru the drivetrain (transmission slip)
breaks calipers hanging REALLY bad.

Texas_WS6

iTrader: (9)

I have never liked my exhaust system. I did remove all of it this past weekend in preporation for the turbo. It does act like the exhaust is plugged. while removing it I looked for glogs in the piping and I did not see any. The muffler was a Flowmaster 2 chamber, I have yet to inspect it to see if it was plugged. I now have the cast manifolds on the car and I have the new SLP Y pipe on it with the cats removed.

The TB is going 100% open, it shows that in the data logger and I have verified that by watching the blade.

I have preformed the "Balance Test" that is a part of my Data logger (HP Tuners) which is supposed to give you a sign of the cylinder health. I did not see anything that looks like it was out of the ordinary. That said it is only a test at idle, I am still running the factory coils. I do not see any signs on the data logger that would indicate cylinders missfireing at load and at Higher rpm. I still have the factory missfire settings, it is not throwing any codes. I would think that a missfire would throw the WB off (I know it will do this in the industrial engines I work on every day), and I see no signs of that.

I just don't know, I am at a loss here. I hate to spend another $400 on a cam, just to make the same power, but I can not think of any thing else that is causing this.

Texas_WS6

iTrader: (9)

I have not checked the voltage at WOT, nor am I sure were to check it at. Please post some advise on doing this.

Ignition is stock coils, MSD wires, I could see the coils can be the problem, how would I verify this?

Injector duty cycle never goes over 71%.

Intake restriction, I am still using a whisper lid with a K&N air filter, no MAF sensor, 4" rubber hose to the 92MM throttle body, and I am using the Edelbrock elbow picture to the left.

Spoke of the exhaust (I will look at the muffle tonight).

Valvetrain, thats the way I am leaning.

Brakes are new and I do not think they are dragging, Trans does not show any signs of slipping, Noise, no the car does not make any unusual noises.

MY99TAWS6

iTrader: (3)

I was talking rwhp of 400 to 450minimum which would be about 500 to 550engine. I can't see you getting much more on l92 heads maybe with afr or trick flo bit more expensive heads. And auto of course lose more power than m6 cars.

Your altitude density air is nasty. What as your buddies mph. Maybe his car is quite a bit lighter. ?

Dyno can correct for alitude so that would give more exact readings.Turbo is going to do good at altitude. Also 408 is not going to be that much faster than 346 but will of couse have more torque .
The cam choice maybe part of the deal and changing it with the turbo sounds like a good plan. I would still think you should be over 110mph but would have to input correction numbers to see how it compares to say cars at other alittudes. Typical 420 hp heads,cam ,headers bolt on 346 up at our track runs around 118mph in a 3600 or so raceweight combo. That is m6.

Turbos are fanatastic at altitude so I wouldn't be worried too much. Your high compression will limit boost and timing a bit but you can of course run meth or alc injection to help out there. Or race gas. Or e85 if you have it there.

Texas_WS6

iTrader: (9)

I agree with all those points. I Think the problem is a combonation of several things, 1-the car is heavy, 4000 pounds with driver. I am on a diet but the car will not be, 2- My alltitude and our DA being always 5000+ feet, 3- The present cam having very lazy ramp rates, and 4- probley an issue with the muffler.

I have the car in the air and I am presently installing my turbo kit. I have to drop the engine back out in order to weld a oil return on my pan. While out I am going to inspect the bottom end (why not, I did not build it so I want to check it so I feel better). At that point I can replace the head gaskets with thicker ones to drop the compression a little (do not know how much it will drop it going from a 0.040" to what ever is avalible maybe someone can tell me), it would also be the perfect time to replace the cam with a very good turbo cam (Comp sugested a 246/256 on a 114) and replace the valve springs to match the cam.

So now we have gone full circle,,,, what cam should I go with? I am all for custom ground cams. I like the large cams, but I do not want to buy one so large it will not work right. That is my conserne with Comps sugestion. They say the larger cubic inches and the L92 heads like big cams.

What say you?

MY99TAWS6

iTrader: (3)

Here is a simlar size engine with afr 225 heads same as mine with gt7 cam which is mellow and is same one I have. Compresson not sure likley 9 or 9.5 to one. He don't have fast 90/90 like me either and these are twin aps kits not single but wanted to show some very nice numbers are doable with mellow cam.I put in 1.8 in mine to get the lift up to 590 or so but have baby duration and high lsa.

re are the Hp setting:

1.606rwhp -640trq - 7.6 psi. 91 pump gas ( my wife drives the car with no problems

2.656rwhp -670trq 9.0 psi

3.707rwhp -773trq 11.6psi

4.736rwhp -812trq 13. psi



car makes 735rwhp(over 840 HP at the crank) on 13psi 812rwtrq(over 900 TRQ at the crank) ..car is a beast. will do the 1/4 LOW 10'S AND over 138+ mph.

Cam dont seem to be hurting him much.

Texas_WS6

iTrader: (9)

So were is the recomedation on the cam from our sponsors? I am looking to buy the right cam for this engine, that is why I posted this thread. Come on lets see your salesmanship. I am stunned not to hear from our sponsors.

engineermike

I think I see the problem...well, A problem at least. Years ago, I had a 310 rwhp combo that gained 40 rwhp and 4 mph by changing from a Flowmaster 2 chamber to an SLP straight-through muffler.

engineermike

No, your parts are right to make 550+ fwhp.

engineermike

NOT that one. That cam would put the rpm of your 408 way up high, where the little 76GTS is out of breathe. You should cam it to peak at 5000 rpm or so, because backpressure will skyrocket at the high revs.

I'm kinda surprised more people haven't chimed in warning you about backpressure issues with that displacement.

Texas_WS6

iTrader: (9)

I do also plan on uping the turbine section to the largest one for it, I think it is a .96 or so. 5000 is way low, my stall is a 3600, I realy do not want to change turbos, but if I need to I can. Are you still running the 76?

MY99TAWS6

iTrader: (3)

Well what do you want in a cam.Do you want lope.Then have to go lower on lsa like epp cam think is 115? Do you want to go higher lift..Aps had good results running lingenfelter gt 11 but then you are likely going to be changing out valve springs frequently. Most people like standard splits these days somewhat close together.
Some like no split and some like reverse split. Problem is not that much actual back to back testing with turbos on dynos .I would like to see mag test a bunch of cams in same engine.

There is ls1 dyno book that has some FI cams.
Basically you can make decent power with just about any cam you are not so much effectiing total power usually so much as powerband.

As I posted that same size engine to yours and mine got great torque and good numbers with that pretty mild gt7 cam in there. Some 1.8 and they are safe on that cam and it would likely do better still.

If didn't have my current cam would likely go to something like 235/240 600 600 with 1.7s and maybe a 116 lsa mabye 115 if wanted a bit of lope. But hey you will get 100 different answers on cams.Pick your general needs for lope and lift then duration don't need crazy to make decent power. Power is mostly coming from the turbo.Or turbo and spray ..they can play nice together.

engineermike

Yep. T76GTS .96 front-mount on a 388 LTx with a 224/236 cam. It peaks at 5800 already, plus yours has bigger heads and higher reving intake manifold. My backpressure peaks at 2/1 at 17 psi boost.

Texas_WS6

iTrader: (9)

Sponsors please chime in here.

Texas_WS6

iTrader: (9)

What happened to our sonsors? Cam experts?

stevieturbo

Sounds like you need a tuner, as opposed to an answer from a sponsor.

Who has been tuning it so far ? And whilst tuning can be carried out at the track....to a degree.

I think in this instance, you really need to get to a dyno.

Texas_WS6

iTrader: (9)

I am the tuner. I have been tuning it in SD open loop. As I have stated before, I have tuned it starting at 10:1 AFR and I have slowly brought it up to 12.8 afr and due to the fact it will not build any heat on the EGT (I have two on the car and it never gets over 950 degrees) I went ahead and hae taken it to 13.8 afr. I started the timing at 22 degrees total and worked my way up to 32 degrees total. The car runs its best 60ft, et, and trap speed at 12.8 afr, and 29 degrees of timing, and a best 60ft of 1.85. I data log every pass and I can tell you it is not running out of fuel, injector, or pulling timing. What else is there to work on in the tune for max power? Air, fuel, fire, all at the right time correct? I still do not see how a chasis dyno is any better then a track. Now an engine dyno, sure, but a chasis dyno?

I am not apposed to getting with tuners and going over the tune, I have actually done this. There might be 20hp to be had in the tune, but there is not 150 hp lost in it somewhere. No there is something wrong with the engine, the combo. I have checked everything mechanically that can be checked without pulling the engine out and taking it apart and can find nothing wrong except the lazy ramp rates of this cam. I guess I am going to have to pull it out and apart next.

stevieturbo

I can see your point.

And whilst I dont use a dyno myself....a dyno does offer a much better controlled environment, and you can pick up small improvements much much easier.


Are you definately running on all 8 cylinders ? Have you tried pulling plugs after a good hard run ?

Can you log EGT's on each cylinder ( even if it is only one at a time )

Valve spring seat pressures all correct ?

Exhaust blockage ? Can you measure EGBP in any way ?

Is the throttle definately opening fully ?

Could there be any form of intake restriction