[solved] Only 120 hp after tune - looking for some help
 

I've got a 1999 ST5 car. I'd like to make about 160 hp, naturally aspirated. I thought I had the right combination of bolt ons to get to at least 140 hp, but it only dyno's at 120.

Please help me find the missing power. What am I doing wrong?

Specs:
BP4W rebuilt by me (could be part of the problem) - recent cold compression test (187, 182, 190, 170) - all valve clearances recently checked
Racing Beat Header - this is getting ceramic coated
Springfield dyno inspired exhaust
22" intake runner with k&n cone filter - adding an airbox to shield it from the headers - tuning shop found 5 hp by just adding a cardboard shield to the engine bay
skunk2 intake manifold
MS3PNP
Innovative wideband

I'm attaching my logs from a recent race, and my current tune. I had it dyno tuned by a shop. Before the ecu, tune, and intake manifold, it made 116 hp/116 torque. After tune and intake manifold, it makes 120 hp/109 torque.

Can I get any more hp through tuning? Do I need to aggressively deck the cylinder head? After that, do I chase power through the valvetrain or pistons? I'd like to do this as efficiently as possible.

Thanks! This forum is awesome.

I'd say something's wrong. You've got decent compression, but that's about 5-7 degrees more advance than I'd typically run. I may not be getting all of the power out of my naturally aspirated builds, but I also get 135hp out of bone stock junkyard VVTs and stock headers. A now illegal Spec Miata head, RB header, and nothing nearly as loud as your springfield dyno exhaust netted me 148hp. That was a VICs intake manifold too. What was your break-in procedure and how does your oil look?

Same dyno? Both runs weather corrected?
Did you touch the timing belt at all?

Are you running stock cam gears or are they adjustable???

Curly, thanks for the reference data. It's been years since I broke in the motor. If I remember correctly, I did a series of 2nd gear pulls. The oil has the occasional metal shavings. I had a hard time sealing up the head gasket, after the initial build, so I went with an MLS and added ARP head studs.

The 116 hp dyno run was in Houston, the 120 hp run was in Cresson. I'm not sure about weather correction. I'm running stock cam gears. The timing belt was refreshed during the rebuild, and I'm fairly certain that it's correctly installed. I checked again when I did my valve clearances over the winter.

So, aside from just swapping in a junkyard VVT, what can be done? Could there be power loss in the bottom end? Do I need to pull it apart and blueprint/balance it? Maybe my timing belt is incorrectly installed.

I'm all ears. I've got a few months until the next race, so I've got some time. Thanks.

you have something out of time I bet. that is a really crappy number for your mod list. balance is not the culprit here.

What kind of dyno? (Im assuming dynojet since youre doing it for classification, but just checking)
Definitely double check mechanical timing and base ignition timing.

Also, do you have a copy of the dyno chart? What RPM did it make peak power, and how high did the dyno operator take it?

$20 says you mis-timed the belt

Thanks for all the feedback. I'm definitely going to verify my timing, again. I found this wild dude on YouTube that has a good walk through. It sounds like I'm off a tooth on my intake cam.


Here's my latest dyno. This is with the intake manifold and current tune.

https://cimg3.ibsrv.net/gimg/www.mia...f8402ac43c.jpg

You don’t even make 120! Your sorta make 115 and then at the end it coughs and sputters out an extra 5hp briefly.

That flat hp curve is indicative of...something. Either a major restriction, or really crappy timing.

Yup! That's why I was asking about the timing belt being done. Highly suspect.

Very well. I'll update this thread, after I've fixed the timing. It's gonna be a few weeks.

In the meantime, I'm doing a ton of research on EFI tuning and the Megasquirt system. I'm sure this is going to require some new tuning, once timing is fixed. It's going to be difficult to get it back to the tuning shop before my next race.

Thanks again for everyone's input. This has been very helpful. Running at 20:1 power to weight in a 14:1 class has been brutal :)

Ding ding ding. Ya'll were right. The intake cam was at least one tooth advanced. I wasn't able to start her up and test yet, but I'm sure proper cam timing will help :)

Thanks for all your help. I'll follow-up with new dyno charts in about a month.

One tooth advanced is a lot of overlap.

Minor update: I indexed the crank damper and found that it had slipped a notch. This may explain the tuner's high timing advance. Not knowing that the damper had slipped, I dialed in an 8 degree offset. Now I've created new marks on the damper that correspond to TDC.

I hope to test start this weekend, then find some time on a dyno before my next race, in June.

If the timing marks on your damper are moving then I'd think it was actually failing and not just slipping. Might be liable to fly off especially in a track environment.

oh no! I’ll start shopping. Thoughts on the ATI with 32 point wheel? It seems like that’s the one to get, but there are a few alternatives floating around.

Either that or Fluidampr is a bit more affordable and I think easier to install. Not sure on availability though.

Any updates on this? Just curious about the dampers really...

Yeah don’t run a slipping damper. I had one fly off once

Yea, quick update. I don't have a bad damper, I'm just dumb. The leftmost notch on the nb1 damper should be at the T mark at TDC. Am I right?

When I originally posted this, I thought the mark on the left was supposed to be on the 10, and the mark on the right at the T.

I got the car started, heard a little knock, and shut it down. I think it's the timing belt backing plate. I'll tear it back down and figure it out.