Steve Brule for President ("Part Throttle" on Engine Masters!)

[burbfixer]

Hey all. I watched the latest 'Engine Masters', and wanted to applaud the repeated reference to "part throttle torque/response.
Don't get me wrong. I have nothing but respect for all the racers, engine builders, and dyno operators (many of whom are posters on this forum) whos engines live at wot, and who share what they learn in magazines, videos and discussion forums.
Still, I always find myself trying to imagine how wot dyno numbers - particularly on streetable combos that are expected to do a number of other things reasonably well too, not just wot - might relate to real world driving experience in a given vehicle. That HAS to include part throttle behavior, and Mr Brule included comments on that when they were discussing the dyno results. (165cc AFR heads on a 410 sbf!!)
It seems many if not most on this forum are involved in some form of racing, which is great. You test the limits on the dyno and on the track, and share what you learn. But I believe there are many like myself who aren't involved in dyno testing or motorsports for one reason or another, but are equally interested in making our vehicles perform well - day in & day out.
Again, compliments to Mr Brule, Engine Masters show, and many of the posters here for the excellent information!

[MadBill]

Is that episode 2 x 13, which isn't on their site yet?
https://www.thetvdb.com/?tab=seasonall&id=317237&lid=7

[digger]

the latest one they talk about the the 165cc vs 195cc vs 220cc AFR head ep 12 season 2

[Kenova]

I have always been curious as to what could be learned about an engine by also dyno testing it at 50% throttle opening.
Has anyone any experience with this sort of test?

Ken

[tt 383]

I have wondear thus too. I would think distribution would be horrible, seems a disc style throttle stop like the deadenbear could/would drastically help a part throttle situation but Idk anything about them.

[bigjoe1]

I have done some part throttle dyno testing. The results were very surprising, to say the least. They have nothing to do with street driving in a car.



JOE SHERMAN RACING

[ptuomov]

What’s the objective of part throttle testing?

Figure out how to program a fly by wire throttle? For example for preignition control (spark retard doesn’t really help with preignition, you have to reduce air a little or fuel a lot)?

Or is it to verify that at low rpms and at low loads, the engine is stable and doesn’t surge or bog down randomly, as it may do with plenum manifold and high overlap cams?

[kimosabi]

Yeah part throttle testing is useful for many applications. Boats for example. Or driver engines. You don't necessarily go full throttle just because your going up hill are you...

[rustbucket79]

Part throttle testing get's the end product closer to optimized for the customer. Fuel curve can look perfect at WOT but be rich or lean as hell during the conditions the engine will spend 90% of it's life in.

[burbfixer]

They didn't actually test at part throttle in the show. They tested AFR 165 heads on a 410 sbf. When it performed way better than they all expected, they just included some speculative comments/questions for each other about how they thought the part throttle, tip-in response, and throttle response with the small port heads might be very fun to drive in a vehicle. It was Brule who first brought it up, but later in the show Dulcich & Freiburger commented on it a bit too.
Might not seem too noteworthy for many of the more experienced posters on here, but for me it was good to hear it at least mentioned. They felt the 195 heads were better suited to the engine as far as dyno #'s were concerned. But then there was a small, rather tentative comment at the end of the show that indicated the 195 heads might do almost as well as the 165's in the part throttle/response area too on this engine. For me, these opinions matter, because these guys (and many of you) have actually driven the engines you've dyno'd. The rest of us haven't, but might be curious about the driving experience of a certain combo.
For what it's worth, I've read many, many great threads on this forum that also include descriptions of how a combo or a change to a combo might affect the real world driving experience in a vehicle. Thank-you! This is very much appreciated by someone like me who has the interest in the technology and science, but not the circumstances or cash to actually experiment a whole lot, and may never own an engine that's been on a dyno.

[adam728]

Part throttle testing get's the end product closer to optimized for the customer. Fuel curve can look perfect at WOT but be rich or lean as hell during the conditions the engine will spend 90% of it's life in.

Absolutely. While not automotive we spend very little time on WOT vs all the drivable areas, whether doing carb or EFI tuning. In the initial cal work WOT is only about 10% of it. After that all the fine tuning, transitions, etc WOT gets even less attention vs say, 1/4 throttle, decels, roll-on, etc. But that's production stuff, not race-only engines.

[ptuomov]

I was asking about part throttle dyno testing. What’s the point? Not to maximize torque at a given rpm, because if you want more torque you open the throttle, no?

I can see optimizing ignition, fuel, and cam timing for minimum BSFC. That would make sense on a dyno.

If dyno time is free, sure, every sort of tuning and sorting out is better done on a dyno. But for a hobbyist with limited dyno time, what’s the part throttle test that absolutely needs to be done on a dyno and can’t be done on the road driving the car with the sensors hooked up?

[Cougar5.0]

I was asking about part throttle dyno testing. What’s the point? Not to maximize torque at a given rpm, because if you want more torque you open the throttle, no?

I can see optimizing ignition, fuel, and cam timing for minimum BSFC. That would make sense on a dyno.

If dyno time is free, sure, every sort of tuning and sorting out is better done on a dyno. But for a hobbyist with limited dyno time, what’s the part throttle test that absolutely needs to be done on a dyno and can’t be done on the road driving the car with the sensors hooked up?

It's difficult to simply drive my 427W to the gas station without pulverizing the drivetrain due to incessant surging at part-throttle. The engine performs well at WOT, but I haven't yet figured out how to tune out the surging at part-throttle. Cutting timing at light-throttle keeps the engine from winding up so much (like a spring), but some of it is the simple fluid mechanics (reversion) of the system. Even if I don't want a higher velocity (lower HP) port, I am curious as to how much that is affecting my ability to tune it at part throttle.

427W, AFR220, 2924 supervic, EFI, 247/250 110LS hyd roller

[MadBill]

The last such issue I tackled (reported in S/T some time back) was a 720 HP twin Edelbrock-carbed 572" Hemi. The owner had jetted up (well, 'needled down' to be precise..) and retarded timing trying to cure a bad 1500-2500 RPM, surge, just as described. With a combination of luck, a 60 year old King exhaust analyser and experience, I leaned out the 60 MPH cruise from 11:1 to 15.5 and added 14°of vacuum advance via a Crane adjustable unit.

Not only did this cure 90+% of the surge, he reported that on his next highway trip to a regular destination, he just made it there and back on one tank when previously he had to refuel at the other end.

[ptuomov]

The last such issue I tackled (reported in S/T some time back) was a 720 HP twin Edelbrock-carbed 572" Hemi. The owner had jetted up (well, 'needled down' to be precise..) and retarded timing trying to cure a bad 1500-2500 RPM, surge, just as described. With a combination of luck, a 60 year old King exhaust analyser and experience, I leaned out the 60 MPH cruise from 11:1 to 15.5 and added 14°of vacuum advance via a Crane adjustable unit.

Not only did this cure 90+% of the surge, he reported that on his next highway trip to a regular destination, he just made it there and back on one tank when previously he had to refuel at the other end.

This can be done off the dyno, right?