Mythbusters - engine & dyno edition

[dieselgeek]

Never is on my end Scott, sounds like we need to take my junk to Toms and baseline it.

That is an interesting idea, maybe there is something about having a complete powertrain attached that changes the results.

Then to the track and move timing up in low and down in second and high see what we do in real life. Return my call LOL I got some questions, I knew you when I got call backs LOL

Will call you right after work, no worries! I'm not famous. LMAO

[JeffMcKC]

I am thinking I would like to leave it on gas with my EMS Pro and tune then switch to the E-85 and MS3 to see what it makes difference

[dieselgeek]

question scott if a turbo car makes max power at the salt flats at 40 lbs boost and 30* timing do you run 30* timing for 4 miles because the 15 second dyno pull says it made the most power there or does the heat come into play so you have to cut it back as temps raise to keep the same power as at the start of the run.

I have hard data that refutes this by a lot. We used to "pull timing" on Gary's Studebaker - twin turbo BBC at 20+psi - and all it did was overheat the exhaust valves, cause the guides to swell up, and hang the valves open. Two years in a row it did that before we learned that you MUST keep the timing ADVANCED on a turbo application because it keeps the heat in the chamber, instead of burning the charge as it goes into the exhaust. I know it seems backwards but the EGT measurement proves this. N/A engines don't mid as much but when you're pushing exhaust into 30+ psi backpressure, that heat has nowhere else to go.

Combustion heat is the same with small changes in timing, the difference is that it's still burning when going out the exhaust if you retard timing and you can see this on EGTs. Our N/A car at Bonneville showed the same data. I leave the timing in it now. Either the engine is built to take the heat or not - I seriously doubt a pro stocker has problems with heat management in a 6 second pass.

If Pro Stock allows EFI - I am doing my best to be set up to work with a couple teams, maybe a top team, on the EFI program. This is a huge goal of mine.

[TheSilverBuick]

Return my call LOL I got some questions, I knew you when I got call backs LOL

Yeah!!

I tried getting him to call me today too Work is keeping him off the phone =P

[Barry Donovan]

I have been confused since the boxer..
I do agree with TC..the once upon a time tale of just locking out distributor, let the big gulp do what it will.
even the hp equation:
(5252xhp) / rpm

on my own little engine it is 50 to 80 more foot pounds than the equal sized inline four.(air fuel, pistons everything)

(5252x100) / 5200

this equals 101. my own is headed for 150-180.

progressive timing has been great, the old vacuum port. another exmple of weird and boxer..needs a teaser timed in. retarding or advancing? I don't know..no computer. today fuel pressure cramming seems to be the difference. my dad and his 550 cat lately now at 90psi fuel..world of different engine. same everything else.

[Ron Ward]

Scott, I have another question. Yeah, I know... I'm full of 'em (among other things) but you have piqued my curiosity.

In the example of a pro stock engine, what do you do on the dyno to account for the pressure above the carburetors created by the large by huge scoop sitting on top of the engine at 200 mph? Would the pressure difference inside the scoop between zero mph and 200 mph dictate a change in timing?


Ron

[JeffMcKC]

I have hard data that refutes this by a lot. We used to "pull timing" on Gary's Studebaker - twin turbo BBC at 20+psi - and all it did was overheat the exhaust valves, cause the guides to swell up, and hang the valves open. Two years in a row it did that before we learned that you MUST keep the timing ADVANCED on a turbo application because it keeps the heat in the chamber, instead of burning the charge as it goes into the exhaust. I know it seems backwards but the EGT measurement proves this. N/A engines don't mid as much but when you're pushing exhaust into 30+ psi backpressure, that heat has nowhere else to go.

Combustion heat is the same with small changes in timing, the difference is that it's still burning when going out the exhaust if you retard timing and you can see this on EGTs. Our N/A car at Bonneville showed the same data. I leave the timing in it now. Either the engine is built to take the heat or not - I seriously doubt a pro stocker has problems with heat management in a 6 second pass.

If Pro Stock allows EFI - I am doing my best to be set up to work with a couple teams, maybe a top team, on the EFI program. This is a huge goal of mine.

Welcome to my Web said the spider.

I knew thats where it would go, this is why in the first post I added at the end, "I think it may be better to say we are over timing first gear and bringing it back to the dyno's best as we go down track." Pulling timing is just the term, I am not trying to say pulling timing from the dyno timing "Best HP" we only do that to hook it up when needed.

Remember Scott, the ProStock guys fight for thing that will improve ET

[JeffMcKC]

Scott, I have another question. Yeah, I know... I'm full of 'em (among other things) but you have piqued my curiosity.

In the example of a pro stock engine, what do you do on the dyno to account for the pressure above the carburetors created by the large by huge scoop sitting on top of the engine at 200 mph? Would the pressure difference inside the scoop between zero mph and 200 mph dictate a change in timing?

Ron

Ron I know this will sound stupid but the prostocks use Dyno Carbs they are not even the same size because it changes at the track. The Jetting and air speeds are taken into account

[Ron Ward]

Ron I know this will sound stupid but the prostocks use Dyno Carbs they are not even the same size because it changes at the track. The Jetting and air speeds are taken into account

Jeff, what changes at the track? I am unclear here.


Thanks,


Ron

[dieselgeek]

Ron, I was told the same thing Jeff is saying, that the carbs for dyno testing are different than those run down the track because G-forces, incoming air pressure all change from dyno testing.

Maybe that's the REAL reason for pulling timing, because that's what an engine wants (think of a turbo engine that is just cresting 100kpa, or getting into the first psi of boost - it wants timing to be retarded, just a little bit).

But SO many people think that you pull timing for better mph or ET. I can see pulling timing for traction reasons or chassis issues only, at the launch. I know that the stock eliminators I am working on now, don't see an increase in manifold pressure going down the track because that is data that I am able to look at. Can't speak to the Pro Stockers - yet...

[JeffMcKC]

It would be very cool to see if once at the track in low gear add 2* from say 5500 to 7500 and then back it up to the max HP * and then leave it alone and watch the 60' and 330' once they have a baseline.

[TC]

I know a lot of sport bikes use different spark tables for different gears, but I suspect that's to help keep it rubber side down in the lower gears.

Traction Control via, timing control??..........

[Ron Ward]

Jeff.... Do you run an air cleaner on your car? Does Jake?


The reason I ask is I'm wondering if in your cases you are dealing with the fuel standoff above the carbs being blown away and experiencing a lean condition at the top end, thus requiring a change in timing.

Just thinking out loud here and trying to get my learn on.


Ron

[JeffMcKC]

I see a lot of guys who buy "Out Of Town Motors" or "Lease them" they cant touch the tune or wont for fear of the Builder not may free thinkers. This is why inhouse cars are the quickest most of the time. Not many big inhouse programs

[dieselgeek]

It would be very cool to see if once at the track in low gear add 2* from say 5500 to 7500 and then back it up to the max HP * and then leave it alone and watch the 60' and 330' once they have a baseline.

Launch control is never the reason I hear for why this timing retard is done. The reason I hear is "because if the engine is changing RPM rate faster, you need to ignite the mix earlier to have the peak cylinder pressure end up in the same place"

that's the myth that's been busted here. Using timing for launch and traction control is not what I was getting at, but a fun topic to discuss, so have at it!