So I went back to the Dyno today. After my first tune, he only did the WOT tuning, I found my VE tables and all to be pretty far off. So, I readjusted pretty much every single table.

The only difference between this dyno and my last one was my tuning and the K&N CAI and homemade elbow. He did adjust the PE and Spark tables from what I had plugged in.



I gained a bit under the curve. Peak stayed the same though. The dotted line is from the last dyno tune he did. Same dyno different day. Correction factors were about the same though. WCF was SAE 113.4%.

But, this is where it get's interesting. The Dyno was reading my RPMs wrong. At 6100, according to the dyno, he hit the 6400rpm rev limiter. I had him raise the limiter to 6700, ZERO valve float!!! It held steady. Not too shabby for SA RR's me thinks.

Anywho, the interesting part is this. Mustang dyno's use torque at RPM to calculate horsepower. So if it's saying 357 ft/lbs at 6100 rpms, but I'm actually at 6400 rpms doesn't that mean the horsepower graphed is wrong?

And since this particular dyno measures actual torque, then the 357 it measure is correct, but the 6100 rpms is wrong. I witnessed this first hand, the dyno read 6100 and stopped while my engine read 6375 (according to the data log).

If that's the case then it should read 433 rwhp SAE corrected instead of 414? Anyone with more experience on the dyno want to chime in?

I know the dyno is a tool for tuning, and it drives like its got more power under the curve for sure, but how do I go about correcting the RPMs?

Worse case scenario, I go to another Dyno to do a few pulls to see what that one says.

 

Nice numbers. A4 or M6? What's all done to the car?

 

LT1 LE2 355, 11.8:1 SCR, Lunati 230/238 .565/.565" 110+6, 1.6:1 SA RR, LT Headers with ORY, T-56, stock 10 bolt.

Build Thread.

The Dyno tuner did sync up the RPMs at 3500 engine to rollers. But it seems the program thought my final drive ratio was 3.28:1 instead of 3.42. Which would explain the rpm discrepancy.

Anyone else dealt with this before?

 

I don't know much about tuning but I agree that's pretty cool the self aligning rockers are doing just fine. I think people do underestimateba good self aligning rocker at least to an extent. I guess those springs on the heads are doing their job too. After all Lloyd did set those springs up for that cam specifically.

 

Yeah Lloyd certainly knows what he's doing. One day I'll get a 52mm TB and ported intake.

 

Yeah at your power lever there is probably 15-20 hp to be had adding a ported intake and TB.

I sold a throttle body to a guy making similar power as you a while back, he shaved a tenth off his 1/4 mile going from 11.28 to 11.17 IIRC so certainly a difference. Don't think he had a ported intake either.

 

Horsepower is always a function of torque at rpm.

Hp = tq * rpm /5250.

That's why you always see hp and torque cross at 5250. You said he was reading 6100 but you were actually at 6400, do you mean the tach was at 6400? The tachs on these cars read high, if he's got the correct rear gear and gear ratio of that gear of the trans he did the pull on, the rpm of the rollers will more accurately tell the rpm of your engine than your tach. By your graph with your cam and heads I'd believe you were at 6100 rather than 6400 since you still hadnt peaked your hp curve, that cam should level off and really peak at 6400-6500 then slightly drop off to 7000. If you were showing 6700 and he was showing 6300-6400, that's where SA rockers get sketchy, NSA vs SA rockers doesn't change the amount of valve float, the danger with SA is that if they DO start to float, the SA rocker floating (not in contact with the pushrod and valve at the same time) is that they can rotate and spin off the pushrod, then when the cam pushes the pushrod up on the next cam rotation, the rocker isn't there to transfer that motion to the valve, instead it sends your pushrod through the valvecover and out your hood. I still think you need to get some NSA rockers and spin it all the way to the fuel cutoff at 7100. Removing the rev limiter and just letting it go until it stops, then see who's reading of rpm was more accurate, because he will probably read 7100 when your PCM cuts fuel and it stops. That cam, your bottom end, and Lloyd's valvespring choice should be good to the PCM limit, and like we discussed on ls1lt1, you need to shift at closer to 7000 for best 1/4 times to make sure the torque of the next gear * ratio at that rpm is greater than the torque of the current gear * ratio at that rpm

http://www.ls1lt1.com/forum/lt1-%7C-...hot-cam-3.html

By the way, nice numbers! Especially for a mustang dyno which are known to hurt feelings. My brother only put down like 330 on his streetsweeper cammed LS1 after being dynotuned on a mustang dyno.

 

This isnt an LT1 or anything like your engine, but this is what Id want to see your curve look like, to take it all the way until it falls off, could be close to 7000rpm, but I wouldnt do that on SA rockers IMO.

 

That's too bad the tuner mis-inputted your final drive ratio. From the thread at LS1LT1 one of your goals was to run the rpms out to help choose shift points, but this session didn't accomplish that exactly. You're making nice power. The SA rockers work good as long as the valve springs maintain control of the valves but when they don't there is no safety net.

 

The RPMs compared are the dyno rollers calculated engine RPM's and the data log RPM's (plus the 6400 RPM cut off kicking in). The Tach has been re-clocked so it's closer to actual, but we all know that the tach isn't off linearly. I don't use the tach in scenarios like this, too confusing.

He synced the rpms at 3500 before the run. But the final drive ratio was slightly off in the dyno's program.

I wanted to see if I actually got valve float. I don't think I will honestly. Seeing it spin to 6700 easily was surprising to me. It's too bad he didn't print that pull out, it was the last one we did and it took quite a bit of convincing to get him to do that. It's annoying actually. And the pull he did to 6700 showed 417hp @ 6400 (dyno rpms). I'd imagine by 7000 it'd be dropping at least a little bit.


That's what I wanted to see too. Although he didn't print it for some reason. He did do a pull to 6700 rpms. The power leveled off to 6700. We didn't go any higher. He was nervous to go to 6700 because of "rod bolts" (his words). I told him it's forged and ARP, then he upped it to 6700. Still haven't done a 7000 pull yet. He seems hesitant on it.

I specifically told him I was looking for valve float so I can set the limiter below that for shift points. He wasn't comfortable going over 6700, he didn't say this directly, but I could see it in his face. I don't think he's used to those older SBC revving that high.

Right?! I did do a bunch of re-tuning since the last session. So he was able to get my WOT AFR's from the 14's down to the 12's. My Commanded timing this time is 33° advanced instead of the previous 26°.

Before I did this I watched a bunch of slow motion video's of valve float. I have faith that with the springs I got valve float won't cause damage if I find it on a dyno then limit the engine below that. I only have another 400 rpms before I run out of PCM, but we all know 50 rpms can go from stable to float.

When I'm due for Valve springs in about 10K miles I'll go the NSA route on bigger studs. But for now I have no reason to worry with the 6700 redline it's set at.

 

I was thinking more like 5-10 for the TB and 10-12 for the intake. So, about 15-22 for both.

But all that will wait for the rear end to get built first. Then Corvette brakes, then TB and Intake. Then N2O years down the line.

 

Yep just like I said. 15-20 for both not each. And 5-10 hp for the throttle body is probably a little light to be honest. A tenth on a car running low 11's is probably more than 5 and maybe more than 10 hp. And we've got a car that runs great here with a stock TB and intake and it's loads of fun. No harm in staying like you are for a while so you can build a rear end.

 

That's the plan! Glad you sold me the parts! It's a ton of fun to drive for sure and it drives great for a daily driver too. Gas mileage is about 14-16 city 26-28 highway.

 

Damn that's good mpg for a cammed lt1. I have the same springs as you right now, the Howard 215s and I just didnt trust them enough for the cam I bought similar to yours, 230/240 .600/.602 on a 1.6 so I got duals to not worry at 7000. I'd love to see what you can put down on a track if you can get a 1.8x without popping the 10 bolt. Some bias ply 26x10.5s should soften the blow more than radials, but I still can't say how impressed I am that you put down those numbers on a mustang dyno. Your trap speed will tell the real story.

 

A mustang dyno, while normally a heartbreaker, can be run in "dynojet" mode, or anything along those lines if the operator so pleases.

 

My best trap so far was 108mph on the 1/4 at 6200DA. Race weight was 3714. That was before this last dyno run, but I don't think it'll change much. If I can get that launch down it'd be better, but I'm way too easy on that rear end; I'm afraid I'm gonna break it.

 

This. Mustang Dyno's have so many variables the tuner can adjust. I'm not sure I trust his numbers after this and his RPM's being off. What else was set up wrong?

 

That's pretty brutal DA. What is the elevation at your track?

 

I got the wrong DA there, different day. The 108.4mph trap was at 5800DA, the 6200 DA was 106.5mph (this trap had the car running 14:1 AFR and 26° timing).

Track elevation is 3075ft.

 

Gotcha. A 400 rwhp M6 F-body at 3,700 lbs should run 115 in the quarter in reasonable DA. I've been through Arizona, so I know how hot it gets. Hopefully that DA will calm down a little bit so you can see where it's really at.