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I just finished swapping a 5.3 truck motor ( LH6 ) into an RX -7 and am underwhelmed with the Dyno results. I did a DOD delete and cam swap ( Crane 224/232 .590 115 LSA ). It has 2.5 in exhaust with Camaro manifolds and a cold air intake. Stock truck intake and GM performance MAF. It only makes 320 to the rear wheels at 6000 and HP drops after 5200. I'm told that approx 20% loss thru the grand and drivetrain is "normal" so approx HP at the flywheel would be approx 380ish. Does this sound about right to you guys?
What valvesprings are you using? Is the graph smooth?
Could be a restrictive filter maybe? You can check by logging engine off key on MAP readings and comparing to WOT MAP reading, it should be within 2-3 kPa at most.
What about fuel pressure at WOT under load? Injector duty cycle?
The HP number itself seems plausible but the 5,200 RPM peak does not. A cam that large I would expect to build power above 6,000 rpm.
The HP number itself seems plausible but the 5,200 RPM peak does not. A cam that large I would expect to build power above 6,000 rpm.
This is more what I meant on my first reply. I just didn't finish the thought very well. Grip, if it helps, here is my dyno from the cam I described below:
Last edited by Darth_V8r; Oct 27, 2015 at 04:53 PM.
power peak does seem early , was the cam degreed ? that truck intake may be part of it also trucks make power early and fall off usually for towing/load carrying ability.
no wideband on the graph , what does the afr at wot look like ?
Thanks guys. I guess there could be a few causes. The valve springs are Trick Flow 16918. They are 1.290 beehives that should be good with the .590 lift. I did not degree the cam.
The fuel pump is a new bosch 044 in tank with a Corvette fuel filter / regulator set up. I haven't looked at fuel pressure at top end because I have not driven the car. I did use the factory hard fuel line from the back to front and it is only 5/16". I wonder if that is part of it. It is not street legal so it was trailered to the dyno. Same with injector and MAF info. I have no idea.
My graph curve looks like yours until about 5200 then tapers down to 300 at 6000. Torque is pretty flat from 4-5000 then dips to 265 at 6000.
AFR's were lean as hell before the tune. After tune, 13:1 to 12.5:1
That double hump and early peak is just like mine. Here's the bad news - my cam was off. It was what triggered my build. I eventually determined the timing set was nine degrees advanced.
I am looking to race this in a series that is "supposed" to be budget minded. I know, right.
Anyways, there is a likely chance that the sanctioning body will have issues with the build no mater what. 320 hp in a 2800 lb car shouldn't be too bad. It gives us something to build on after a few races.
Yea could very well be the cam, I always degree mine in. I've had some that were ground off, and as others have said with an aftermarket timing set, it could be off as well. If you are still using the stock truck intake you might want to switch it for a car one, that will definitely move the powerband down.
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HP expectations? 
