Is my cam too big?

[72turboz]

Hello all,

First time poster, long time lurker.

 

As the title states i am wondering if my cam grind is too big for what i want out of it. The car is mainly now going to be street driven with occasional track use, car has a L28et.

 

The cam specs are as follows; @015 TDC, Intake opens 33, Exhaust closes 33, Overlap 66. Intake Closes 77, Exhaust opens 77. Intake Duration 290, Exhaust Duration 290. Intake lift 540, exhaust lift 540. 112 LSA.

 

I also believe i have Isky springs installed but need to double check, small chance they could be new oem springs. Also have brown L28 valve seals installed but plan to replace them with the ford Vitron seals from Felpro.

 

Heres the overall specs of the car; l28et block with ITM dished pistons 30 thou over, Holset He351cw turbo with wastegate welded shut, stock intake manifold and stock exhaust manifold modified to fit a F38 external wastegate. P90a head converted to solid lifters, no port work, plan to have the head CNC ported in the near future. 440cc injectors. FMIC. 2.5 inch charge pipes. 3 inch downpipe into 2.5 inch exhaust, plan to have full 3 inch in near future as maybe this is choking power. T5 transmission, long nose R200 with LSD, 300zxt axles, disc brakes all around. Car is tuned on Megasquirt ms2 and runs great when warmed up, need to install a idle control valve for cold start. This is the general setup of the car right now.

 

So the big question, on the dyno the car made 270whp at 12psi but as we tried to add more boost and/or timing the power did not increase, dyno showed flat power from 4000 rpm to 6500 rpm. No wheel slip or clutch slip was observed. Is my cam too large? Causing valve float? Typically you see variations in power or power dropping off with valve float but the dyno was reporting a horizontal line holding till 6500. Car runs great and is healthy, just cant get anymore power out of it with timing or boost.

 

I am just curious as to what you guys may think is going on. Is my 2.5 inch exhaust causing too much back pressure and choking the car at high rpm? Do i need head work and porting to make the current cam work? Something is happening and before i go digging into the car chasing an unknown issue i wanted to get more opinions.

 

My general thoughts are to put a smaller isky or robello cam in, or find heavier springs for the current cam if its worth keeping it in, i will more than likely have the head CNC ported, and increase the exhaust to a full 3 inch at the same time.

The car is a blast to drive, spools up at around 3400 rpm and holds till redline, but i was aiming for 300-350whp when i built the car/engine so naturally im slightly disappointed.

 

Any thoughts or help would be greatly appreciated, thanks guys!

Edited July 24, 2023 by 72turboz

[72turboz]

Just took a look and I have Schneider springs installed in the head right now. Would it still be worth looking at a smaller cam or freeing up airflow for the current cam?

[jonbill]

I don't believe changing the cam will make any difference. Problem is elsewhere. Something in the intake path perhaps.

[Brad-ManQ45]

Put in that 3" exhaust before anything else...

[zboi]

Doesn't sound like valve float. Can you confirm that you noticed increased boost pressure when you cranked it up? The only way you are going to stop making power is when your clutch is slipping, you run out of fuel, or run out of turbo The more backpressure you have, the less you will be able to get from your turbo. If you were out of fuel that would be easily seen by climbing AF ratio. 

[72turboz]

I have since spoken to Ron at isky cams, going to drop off a core for a cam re-grind that better suits my needs.

Went through the valve train and everything seems fine there so that’s out of the question. 
Fuel is good afrs stay consistent fuel pressure checks out.

Clutch is not slipping we verified that on the dyno, it’s a comp clutch unit that was broken in correctly. 
Boost is increasing in the manifold, thats been verified.

I will up the exhaust size to 3 inch next but I can’t imagine the current set up is causing so much back pressure that it’s hindering flow and performance, maybe I’m wrong here.

 

on a side note I picked up a nice n42 intake manifold and throttle body setup at ZCon, so there’s some positive news. 

[NewZed]

On 7/23/2023 at 3:33 PM, 72turboz said:

tried to add more boost and/or timing the power did not increase, dyno showed flat power from 4000 rpm to 6500 rpm

 

Not an expert but what do you mean when you say "power"?  For HP to stay flat torque would have to drop off.  An image of the dyno curve might be helpful

 

Looks like you're focused on air flow through the intake side with your thoughts about the cam.  Have you thought about rigging up a temporary 3" muffler system or just run an open downpipe on a dyno run just to knock out the exhaust side as a cause.  Simple easy test, might show something.  You mentioned the pipe size but nothing about the muffler itself.

 

Also, where are you measuring boost from?  The plenum?  Again, not an expert, but aren't the stock runners kind of small?

 

[zboi]

I take it they looked at rpm vs MPH to confirm clutch not slipping? Do you have an IAT sensor, or knock sensor? If your getting too hot or hitting knock then that is just all that motor can do. Be nice to see a picture of the motor. These engines with reverse-flow heads are real bad for heat soak, you'll want to try to minimize that as much as possible with header wrap, heat shields, CAI, turbo blanket, etc.

Edited August 17, 2023 by zboi

[72turboz]

1 hour ago, NewZed said:

 

Not an expert but what do you mean when you say "power"?  For HP to stay flat torque would have to drop off.  An image of the dyno curve might be helpful

 

Looks like you're focused on air flow through the intake side with your thoughts about the cam.  Have you thought about rigging up a temporary 3" muffler system or just run an open downpipe on a dyno run just to knock out the exhaust side as a cause.  Simple easy test, might show something.  You mentioned the pipe size but nothing about the muffler itself.

 

Also, where are you measuring boost from?  The plenum?  Again, not an expert, but aren't the stock runners kind of small?

 

Both my Hp and torque numbers stay flat all the way to redline, torque does not drop off and hp does not increase. They are also the same number 270whp and 270tq. This trend stays the same no matter how much boost we put into it, 5 psi increase is all we messed with, and timing does not change the output. I will take a picture of the graph and upload it.

Current muffler is a 2.5 hks fart can with the silencer removed, no resonator upstream just the muffler. I thought about removing the exhaust from doe pipe back but figured might as well have a full 3 inch made if I’m going to mess with it and put it back in the dyno. Still the exhaust being the culprit seems off me to.

 

Boost is measured from the intake manifold, so doesn’t seem to be an issue with the intercooler or piping. The stock runners are narrow but people have been getting upwards of 350hp on essentially the same setup that I have. So my thoughts are it’s not intake related. I wouldn’t doubt that the current cam was running out of air though as the grind was for high rpm power.

[72turboz]

47 minutes ago, zboi said:

I take it they looked at rpm vs MPH to confirm clutch not slipping? Do you have an IAT sensor, or knock sensor? If your getting too hot or hitting knock then that is just all that motor can do. Be nice to see a picture of the motor. These engines with reverse-flow heads are real bad for heat soak, you'll want to try to minimize that as much as possible with header wrap, heat shields, CAI, turbo blanket, etc.

Yes he confirmed the rpm against mph and roller loads. Tires were not slipping either. IAT were high 80s to low 100s during the dyno session, averaging high 90s during wot pulls. No knock sensor MS2 doesn’t have the greatest support for that. I also have the coolant bypass mod for all cylinders on this head, coolant temps sit nicely at 180 degrees. The IAT is just prior to the throttle body. Factory heat shield is installed so heat soak doesn’t seem to be the issue. The turbo intake is kicked down and left just outside of the front wheel well to minimize heat from the radiator. I’ll try to upload a picture of the engine. 

[zboi]

It is not possible for HP and TQ to remain the same as RPM increases. Dyno operator is doing something wrong.

[72turboz]

[72turboz]

Roughly what the engine looks like, something’s have been replaced or tweaked since this picture was taken but overall what how it looks.

[72turboz]

55 minutes ago, zboi said:

It is not possible for HP and TQ to remain the same as RPM increases. Dyno operator is doing something wrong.

I miss spoke, having the tuner send me a picture of one of the runs the torque does fall off, he’s sending me a picture of the final 12 psi run, again adding boost up to 16 psi did not yield any gains.

[zboi]

I'm not seeing any heat shields in that picture. Were they taken off? The temps you posted look good, but where is the IAT sensor installed? Air temp could be much higher by the time it gets near/in the intake manifold. 

[72turboz]

1 hour ago, zboi said:

I'm not seeing any heat shields in that picture. Were they taken off? The temps you posted look good, but where is the IAT sensor installed? Air temp could be much higher by the time it gets near/in the intake manifold. 

The heat shields are bolted to the underside of the intake manifold and bolted to the exhaust manifold you can’t see them in the picture. The IAT sensor is on the intercooler piping right before the throttle body, you can see it standing straight up. It’s right before entering the intake. I don’t think it’s heat soak, dyno pulls we’re done with ambient temps in low 80’s here in socal.

[72turboz]

Trying to upload a picture of the dyno graph but it keeps inserting upside down.

 

[NewZed]

Let it load upside down.  People can manipulate it.

[72turboz]

[72turboz]

Adding boost and or adjusting timing doesn’t affect the curve in anyway. Stays relatively the same. Running out of something somewhere. This was at 12 psi if I’m not mistaken.