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So, I got in there and found that the intake cam gear had been reinstalled incorrectly. The guide pin (dot) on the cam shaft had shifted out of place, so when I torqued down the cam gear, it was crooked and resulted in slightly incorrect cam timing. I got that sorted out, and re-verified everything.
I got her started, and the engine sounds great! By far the best sounding idle since I've been working on the car. So, I think we've got the basic mechanical issues solved.
I've got an appointment to have the car tuned, at the end of the month. Then my next race on June 8th. I'll report my numbers, as soon as I have them.
Here's the final update. Jesse found a ton of power. 163 peak hp and a steady 130ish torque through the entire range! I can't wait to go try it out at Hallett!
Thanks again for everyone's help. I couldn't do it without you.
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.
This is interesting. I have been battling a similar issue with my car. I have a vvt swap, skunk2 intake manifold, miataturbo 3d printed intake, jr header and a 2.5 inch exhaust and I can only manage the exact same curve that you did. It's frightening how similar our curves are. I will be investigating my car either tonight or tomorrow for a misaligned tooth somewhere. Here is my chart for comparison. Blue was with the stock catback exhaust and red was with my 2.5 catback.
My N/A VVT car makes 130wtq/160whp on E85 which is more like E75 most of the time. About three months ago I went to dyno tune it and discovered I was down on power. Turns out I was off a tooth at the crank but my dumb *** mis-diagnosed it to be off a tooth at the intake cam so I moved just that. Went back to the dyno and pretty much the same results although not identical. Took off all the covers and damper to make absolutely sure and found my mistake. Went back to dyno and had 130/160 like usual.
In either case, the power loss was about 10wtq/15whp PEAK, at worst. Under the curve numbers fluctuated to even at low rpms and close to 20tq/hp at 7800 rev limiter. Amazingly enough this was the second time this happened. It was about 5 years ago the first time it happened but I wasn't the dumb *** who did the belt that time. In any case, same amount of power loss.
How the OP picked up the power he did by just cam timing does not jive with my results of being *one* tooth off. Mind you, one tooth off at the crank, or one tooth off at one of the cams is what my experience has been, twice. I was nowhere near 40hp down. I would say he had to be more than one tooth off. Or the tune was really bad. Or both.
I'm just sharing my experience so you don't think that the OP's results are what you should expect from a timing belt snafu. I don't mean any slight or doubt to the OP's results. I just don't think they are typical.
I started taking my engine apart. I can always use an extra set of eyes but it looks to me that my timing belt is installed correctly and nothing appears to be jumped which makes things seem weirder for me. What do you guys think?
I started taking my engine apart. I can always use an extra set of eyes but it looks to me that my timing belt is installed correctly and nothing appears to be jumped which makes things seem weirder for me. What do you guys think?
To be sure you need to look at the timing belt crank pulley (behind the damper pulley) and make sure the arrow on it is aligned. Checking the damper timing marks will give you a false positive if the damper has slipped.
Another option is to take the #1 spark plug out, drop a long screwdriver down into it, and watch it while turning the crank pulley. Finding TDC that way is fairly simple -- not quite as accurate as using the arrow, but plenty good enough to check for 1 tooth off. I do this because I have an ATI damper and it's a PITA to remove.
I realized one of my earlier photos had the cams off 180 degrees. Here are the follow up photos with my crank rotated 360 degrees.
It all seems odd to me. It looks like it is all timed correctly but my dyno follows the exact same curve that the OP had and he had his timing off. I verified crank trigger offset and it was spot on to give me 10 degrees actual when I commanded 10 degrees.
Attached is the ignition table I used for the red line and the vvt table I used.
and below is a quick video I took of the play my timing belt had which seemed to be a bit excessive to me. Don’t know if that could be the issue either.
So this is weird because this is the oem timing belt on the engine and it previously was making 150whp in this configuration with vtekkiller. How would it jump like this? I have yet to take it off.
You need to get the camera down lower to be sure. If you're not looking at it straight on, then the parallax error makes it really hard to tell if it's right.
Sorry, late to the party, and I never took the time to look at the posts below the pic..
I don't know much about ignition timing on a VVT engine but it looks like you are leaving a lot on the table with your spark map.
I go into 40+ below the 100 kpa threshold.
05-13-2019, 11:44 AM
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