Dyno sheet thread

[sfdaugherty]

Dyno results for my sr20de s15 Autech. Factory high lift cam and 11.7 to 1 compression ratio. The video is of an earlier run. 161 hp and 139 ft lbs of torque.

S15 dyno 161 hp 139 tq(1).jpg

[

Shannon

[Pjackb]

Dyno results for my sr20de s15 Autech. Factory high lift cam and 11.7 to 1 compression ratio. The video is of an earlier run. 161 hp and 139 lb ft of torque.
Shannon

This is stock Autech right ?

[GoldHawg]

[/quote] This is stock Autech right ? [/quote]

Sans header. Wonder what it would do with a nice SS header? Hmmm. May have to solve that problem real soon. Yes Shannon, real soon!

[sfdaugherty]

Yes. Stock except converted distributor to coil on plug and tuned with Haltech Platinum Pro ecu.

The factory stainless header won't fit in a roadster so anxiously awaiting a header from Jeff.

Shannon

[Gregs672000]

Very nice numbers for sure. I did some comparisons in torque between a few of the U20 sheets, noting where peak torque occurred. I think Brian's sheet demonstrates how a cam, carb jetting and timing (ignition and cam) all work together when it hits it's 'sweet spot'. The torque REALLY picks up between 4000 and 4500 rpms on Brian's motor, jumping about 17 points in this very short span, where as the other U20 profiles have remained close to their peeks. This could be where the C cam outperforms the B when all the other components are aligned (?). It also shows how the C or the " bigger" (more duration) cam hurts low end power even vs the B, as Brian's engine is making 11 less ft lbs of torque at 3500 rpms vs the others. By 4000 rpms they are equal and very suddenly the cam "comes on" and the power increase results. I wonder what an A cam SU engine would make and what the profile would look like in comparison. I would also be interested in what they did during the tuning that resulted in such a significant change in Brian's output... really a big change!

Comparing Brian's U20 to the S15 (variable cam timing Engine? Also much higher compression ratio), at 3500 the S15 has a lot more torque (19 ft Lbs more), but when the C cam comes on, they become about equal. But unlike the U20, which starts dropping off past 5000 rpms, the S15 continues to build torque all the way to 5500 rpm and maintains. Is all this the result of variable cam timing? You see how engineers have been able to "have your cake and eat it too" eh? Can't fight 40 years of technology!

I'm just spit balling here, but I think Brian's motor has come together very nicely regarding cam timing. I wonder how the other two B cam motors might benefit from some cam timing adjustment and likely subsequent tuning changes? Very helpful that all these engines were run on the same dyno. This is great information for one to do some general comparisons, thanks!

Discuss...

[Gregs672000]

I was going through some papers in the closet and I found my old dyno sheet from 2004. This engine was with some head work, Racer Brown cam, EI dizzy, 48mm SK carbs with 39mm chokes. The operator said I was having some significant fueling problems as indicated on the jumpy graph. Because of that I switched to OER Mikuni copies soon afterwards, now with Dellortos. Sorry for the sideways post, if you click on it it's normal. 131.5hp, 130.2 torque. It looks like the engine literally burped at 4000rpm before catching itself again!

[Gregs672000]

So I finally got on the dyno yesterday after fiddling with my carb linkage, trying to make sure I was getting full throttle (it's close but still has a little more movement, not sure what difference this would make). After all my road testing and tuning, I figured it was pretty close... wow, was I wrong! As soon as we got into the pull she started knocking bad, but somehow I had left the laptop sitting on the bench at HOME, so my daughter and son-in-law (who were with me to watch) drove me back to retrieve it. What i thought would be a quick pull turned into a tuning session. Fortunately the operator was GREAT, and began helping me pull out more timing, and more importantly, by using his far better than my cheap Harbor Freight sourced dial back timing light also discovered that my base 20 degree timing was actually 26 degrees ( the "offset" of the crank sensor is adjustable on the megajolt for this reason to give you the ability to "true" it via a timing light, which I had done and adjusted accordingly), so I was running an additional 6 degrees more than I thought throughout the map (ahhhhh!)... gee, wonder why she's knocking! Once fixed, we did a couple pulls, adjusting timing to get her happier (i.e. NOT knocking!) at max torque and limiting timing to 30 degrees to be safe. Unfortunately my A/F ratios were now screwed up (amazing how timing changes effect this), so my ratios were initially 10 to 1 when I hit it, then remained in the high 11s to low 12s throughout the pull (per the operator I want to be in the low 13s) but we didn't have time to swap out carb and accelerator jets, so we were done for the day. But now I have a much better, max torque timing point to work from. The result was about 140hp and 130ftlbs torque (139.32, sheet may be hard to see), and he felt he could get another 10hp with jet changes and final timing tweeks, but that was for another day.

While I would have liked to have rolled up and put down 145-150, I learned a ton from this time. First, 11.7 to 1 is too high a compression for 92 pump gas... I wish I was at 11.0. Second, a dyno is different than the street, as she NEVER knocked like what I heard when street testing, and is well worth the money. Third, I may play with cam timing some as I think it should work better up top than it is (dropping off a bit past 6000rpms), and may go back to the 40mm chokes, from 37mm. Forth, the jury is still out on fitting larger valves, but so far I've seen no specific advantage. Fifth, this experience again has shown that everything is part of a system and it takes time and GOOD data to get them to work well together. Ya can't just throw stuff at it and expect it to WORK! The plan now is to work on the rest of the timing map, change carb jetting accordingly and go from there. Once I think it's right I'll run it again, hopefully a lot closer!

[2mAn]

140whp is a solid number. 11.7:1 is pretty wild but with some higher octane than 92 it could respond quite well, but ends up being a lot more expensive when it comes to fuel costs...

Does Costco sell Octane Booster by the case? hmmm

[sfdaugherty]

Nice numbers Greg.

Shannon

[SLOroadster]

So I finally got on the dyno yesterday after fiddling with my carb linkage, trying to make sure I was getting full throttle (it's close but still has a little more movement, not sure what difference this would make). After all my road testing and tuning, I figured it was pretty close... wow, was I wrong! As soon as we got into the pull she started knocking bad, but somehow I had left the laptop sitting on the bench at HOME, so my daughter and son-in-law (who were with me to watch) drove me back to retrieve it. What i thought would be a quick pull turned into a tuning session. Fortunately the operator was GREAT, and began helping me pull out more timing, and more importantly, by using his far better than my cheap Harbor Freight sourced dial back timing light also discovered that my base 20 degree timing was actually 26 degrees ( the "offset" of the crank sensor is adjustable on the megajolt for this reason to give you the ability to "true" it via a timing light, which I had done and adjusted accordingly), so I was running an additional 6 degrees more than I thought throughout the map (ahhhhh!)... gee, wonder why she's knocking! Once fixed, we did a couple pulls, adjusting timing to get her happier (i.e. NOT knocking!) at max torque and limiting timing to 30 degrees to be safe. Unfortunately my A/F ratios were now screwed up (amazing how timing changes effect this), so my ratios were initially 10 to 1 when I hit it, then remained in the high 11s to low 12s throughout the pull (per the operator I want to be in the low 13s) but we didn't have time to swap out carb and accelerator jets, so we were done for the day. But now I have a much better, max torque timing point to work from. The result was about 140hp and 130ftlbs torque (139.32, sheet may be hard to see), and he felt he could get another 10hp with jet changes and final timing tweeks, but that was for another day.

While I would have liked to have rolled up and put down 145-150, I learned a ton from this time. First, 11.7 to 1 is too high a compression for 92 pump gas... I wish I was at 11.0. Second, a dyno is different than the street, as she NEVER knocked like what I heard when street testing, and is well worth the money. Third, I may play with cam timing some as I think it should work better up top than it is (dropping off a bit past 6000rpms), and may go back to the 40mm chokes, from 37mm. Forth, the jury is still out on fitting larger valves, but so far I've seen no specific advantage. Fifth, this experience again has shown that everything is part of a system and it takes time and GOOD data to get them to work well together. Ya can't just throw stuff at it and expect it to WORK! The plan now is to work on the rest of the timing map, change carb jetting accordingly and go from there. Once I think it's right I'll run it again, hopefully a lot closer!

I'm no where near 11.7:1 compression, but I put 141 hp and 132# feet of torque to the wheels. That is without the fancy ignition system, or high compression. I'd think with your higher compression you would be at least 150 hp at the wheels. Yes, I do realize your carb jetting is now off, but running sky high compression doesn't seem to be worth the effort.

Will

[Gregs672000]

There certainly is a trade off of compression vs what fuel is available, and I agree that 11.7 is too much for the 92 to be optimum, and thus I have to pull more timing out to keep it safe... can't realize the power potential... yet. There's a few things I can manipulate, such as cam timing, choke sizes, jetting to work with the system. I'm not done yet. I do feel that 11 to 1 is quite reasonable with good timing and A/F control. We also don't know what the limiting factor(s) are... who knows, maybe THIS engine needs a different header, maybe it's choking off on the 37s? I just drove it around town, and things are not fully sorted. With this dyno pull I have a place to start...

Will, I'll be eager to see new dyno numbers for your engine when it gets its new head, and as I recall you have an interesting cam as well. Regarding the megajolt, at wide open throttle it's not necessarily any better than a well functioning distributor with the proper curve other than to eliminate some potential for spark scatter. On a dizzy the vacumm advance steps off and it runs mechanical, or in the case of solex Roadsters there is no vacumm advance connected. What the MJ does do is allow for tuning, which is by default required in order to make it work right. The megajolt allows for more control over timing under different engine conditions with the goal of optimizing fuel economy and reducing emissions, as well as to give better driveability. But I have no doubt that my old Jacobs Pro-Street box way out sparked this system. Pros and cons. I need the control due to the engines design because I can't recurve a distributor at home!

[2mAn]

I’ll be putting mine on a dyno I’m the near future too

[SLOroadster]

Greg,
My head isn't going to be anything different. Its the same port job, same cam, ect. It might get new valves since the ones that were in there were 8 different lengths. It will be getting new valve springs. When I dyno'd my car, I was on 91. I was running a 2 inch exhaust and 37mm venturis in the carbs. When I went to the bigger exhaust, and 39, then 40mm venturis, it was a different car. It wasn't till engine rebuild #2 in 2010 that it started wanting 100 octane. Why it wanted 100 after, even though I used all the same parts, I don't know.

Will

[Gregs672000]

Maybe the gas changed, not the engine... the operator did ask me what fuel I was running... "Well, um, Fred Meyer...". He mentioned tuning on a car last week that he was very familiar with but had been filled with Arco 92 (not my opinion, just what he said) and he could not get it to run right until that fuel was out of it and replaced with Chevron... I've never believed ads, but Hmmm.

[SLOroadster]

My engine seems to like Chevron over Shell, my E30 M3, likes Shell 91 rather than the chevron. It also seems to like Mobil 1 fuel as well. Both really like Sunoco 100 octane, but that is expensive.

Yes, cheap fuel can have an effect on how the car runs.

Will