Dyno Day at Jesse Prather Racing

[MiniDave]

Today about 10 of us made the trek to Topeka, to Jesse Prather Racing to use his dyno.

We had 3 Minis, 2 Caterhams, a Bugeye, 2 MGB's - one supercharged, a Spitfire, and an Elva....every car showed substantial improvement when they were done, except the Bugeye - it had a 1275 in it and apparently it was doing everything it could.  ;D

This is an in ground Dyno, and Jess and his dad Kent Prather ran the show.

Every car benefitted from timing changes, some substantially. Several of the cars got new needles or in the case of Weber, new jets. Two of the Minis started off at about 52 HP at the wheels, but when done both were 68-69hp at the wheels, that's a fairly huge improvement - about 30% more HP.

The one Caterham has a 1600 Kent motor and a dual throat downdraft Weber, he gained about 12 hp. John Styers Caterham - John was the organizer of the event - went from 94 hp to 112.

Here's John's Caterham on one of its runs....

I didn't get to see where the spitfire ended up, but it's 1300 was making about 52 hp at the start, and the first thing they found was that the timing was over 55* advanced, it's a wonder it ran!

John's Mini benefitted from some new needles - it was running incredibly rich and once done I drove it back to KC. The car was transformed, way more low rpm torque and it was hard to hold the car down to 80mph on the run home...it just ran effortlessly. Here's one of his runs....

Susan McKensie's car also had the timing out of whack, and you could clearly see the improvement in the curve - it went from a very choppy curve to one that was almost completely smooth - the engine did the same. I thought it ran pretty well when I drove it but an extra 18 hp and considerably smoother engine had to be noticeable.

The final highlight of the day for me was getting to drive Russ Foust's Acura V6 Clubman. Jesse had dyno tuned it a few weeks ago when Russ got it running, and Russ said it went from 150 hp to 230 by the time they were done with it! And OMG was this thing fast! I had another club member with me in the car and he was watching the tach and speedo as I was busy just trying to keep it on the road - to be fair we were on a back country road that was really uneven. I was shifting at 42-4300 rpm, and the Vtec doesn't even kick in till 4500 rpm, and it was all I could do to keep it in control, I can imagine how it runs on a smooth road or track where you can really wind it out! It was surprisingly docile and quiet - I expected a lot of noise with the engine right behind my head but it was actually quieter than my car. So incredibly fast!

The first pic is the dyno run on the Bugeye. the bottom trace shows the optimum and you can see how close the actual performance was to that line. After three runs they decided there really wasn't any improvement to be had and called it good.

The next chart is John's Mini, the yellow trace was the first run and you can see how badly it was coughing and spitting..... by the final trace after timing adjustments and new needles and carb tuning it was smooth and considerably more powerful.

There's also a pic of me in the beast!   :-\

[gr8kornholio]

Is that too far of a drive for the 10 yr picnic?  I bet my 1380 could benefit greatly from this. For that matter, do they only tune in the car?

Looked like a great time. Is that clubman the same one that was for sale on mini mania?  Paint looks the same, but think it was just a front engine vtec clubman.

[MiniDave]

It might have been, but  it had a Vauxhall engine, not a Honda.

It was OMG fast with the V6 back there!

They don't just do anybody's car, the British car club worked this deal - they in essence bought the shop for the day for a price, then sold time slots to the members to make it work.

Kent Prather - Jesse's dad - has the engine shop, he has the out-of-the-car engine dyno.

[94touring]

What total advance and air/fuel numbers were the sweet spot on the minis?

[MiniDave]

Each one s a little different, but right around 34* total advance at 3K rpm seems to be real close.

[John Gervais]

Dave, it sounds like you had a really great day - wish my car was there...

But, you're saying that 34° at 3000rpm seemed to be the sweet spot?  I'd always heard that around 24 - 26° at 3K was closer to what we'd need.

I'd have thought that would be far too much static advance, and way too much by the time the engine gets to 5000rpm.

Here's the Aldon Yellow (classic/common) advance curve.  As you can see, 34° - (2 x 6.8 ) = 20.4° 'static timing, and by the time the engine reaches 5000 rpm (where the distributor finally stops mechanically advancing), the engine will be running on 44+° total advance - unless I've got my thinking wrong.

If the engine was seeing 26° at 3000 rpm (using the Aldon Yellow example), 26° - 13.6° = 12.4° static, resulting in 36.4° total advance at 5000 rpm.

Can you tell us more? 

[MiniDave]

The Mini manual says....

998's - 7*@ 1000, Dist advance 14*(X2) 28 +7=35* total advance at 4K

1098's  9* @1000 rpm, 20-24* @6K rpm =  33* total

1275 GT  13* @ 1000, 18-22 @4K  =35* total

I see a pattern here..... ;D

All of these engines want about 34-35* total advance, the cam wil partially dictate what RPM they want it all in.

I haven't seen any mini engines that want 20* static, most say around 8* static is a good starting point, and to use a timing light to find total advance and adjust accordingly.

[94touring]

Going by that, my dizzy would provide between 38 and 44 degrees advance at reline depending which curve I choose with 1000 rpms starting at 8.  Does that seem a bit high?

[MiniDave]

Yes, I think that's too much advance, Kent runs 24 +10 on his race engines....and they turn 8K.

[John Gervais]

The Mini manual says....

998's - 7*@ 1000, Dist advance 14*(X2) 28 +7=35* total advance at 4K

1098's  9* @1000 rpm, 20-24* @6K rpm =  33* total

1275 GT  13* @ 1000, 18-22 @4K  =35* total

I see a pattern here..... ;D

All of these engines want about 34-35* total advance, the cam wil partially dictate what RPM they want it all in.

I haven't seen any mini engines that want 20* static, most say around 8* static is a good starting point, and to use a timing light to find total advance and adjust accordingly.

Right - precisely why I was curious about the '3000 rpm' bit in your earlier post.

As you can clearly see by the aforementioned graph, the Aldon Yellow continues to advance til 5000 rpm, which would exceed the 34(+/-) max total target. 

To be clear, I'm not sharpshooting -

[MiniDave]

But, does it continue to advance or does it limit? If you overadvance at high RPMs you can cause severe detonation - which can cause real damage to your engine.

Total advance needed also really depends on the engine specs, cam timing, lift, compression ratio, carburation etc....

[John Gervais]

When I spoke to Aldon on the phone, they confirmed the advance data on the chart - the chart is accurate, which shows that the Aldon Yellow continues to mechanically advance until 2500 distributor rpms (5000 engine rpms) where it reaches it's 12° (24°) maximum limit.

[94touring]

Then on your aldon you'd set your static and add to their curve I do believe.  The curves on my csi that I'm installing assumes a static timing of 10, so these curves read actual values. 

[John Gervais]

From when I installed this distributor, I normally just bring the engine to 5000 rpm and turn the dizzy to 34°, though I think it's actually at about 32° right now. 

[BruceK]

Every car benefitted from timing changes, some substantially. Several of the cars got new needles or in the case of Weber, new jets. Two of the Minis started off at about 52 HP at the wheels, but when done both were 68-69hp at the wheels, that's a fairly huge improvement - about 30% more HP.

What an improvement.  I sure wish I could get my Mini on a dyno with somebody knowledgeable about improving its performance. 

[MiniDave]

I'm sure there's a race shop in your area that does dyno - tuning, the problem is would they know anything about SU's, and would they have a selection of needles to dial it in? Maybe the Brit's Bits guy knows of one?

Maybe the folks you took Emma to for the alignment know of a shop in your hood?

If not, make a trip to KC (well, Topeka actually), if they can get similar results to what John and Susan's car got it would be well worth the trip!

I'm hoping to get another dyno day set up for the fall - you don't want to do it when it's 95* and a million percent humidity like it is here in the summer, but you'd be welcome to join us - 8 hour trip from your hood. Maybe Dan would have his hot rod together by then and you both could come up? I know I can get a few folks from KC with classics to go, and Don definitely wants to get the Pup on the rollers. We need about 10 folks to make it cost effective.....I'm sure there are a couple of local Lawrence (Stan?) and Topeka folks who didn't get to go to this session that will come, I'm pretty sure we can get 10 people/cars together.

[BruceK]

I'm sure there's a race shop in your area that does dyno - tuning, the problem is would they know anything about SU's, and would they have a selection of needles to dial it in? Maybe the Brit's Bits guy knows of one?

Maybe the folks you took Emma to for the alignment know of a shop in your hood?

They are nice folks, but more focused on Subarus and Supras.  I don't think they would understand tuning a car without a laptop hooked up to it.  And I think they'd look at an SU they way I'd look at a steam engine.

If not, make a trip to KC (well, Topeka actually), if they can get similar results to what John and Susan's car got it would be well worth the trip!

I think it really would.

I'm hoping to get another dyno day set up for the fall - you don't want to do it when it's 95* and a million percent humidity like it is here in the summer, but you'd be welcome to join us - 8 hour trip from your hood. Maybe Dan would have his hot rod together by then and you both could come up? I know I can get a few folks from KC with classics to go, and Don definitely wants to get the Pup on the rollers. We need about 10 folks to make it cost effective.....I'm sure there are a couple of local Lawrence (Stan?) and Topeka folks who didn't get to go to this session that will come, I'm pretty sure we can get 10 people/cars together.

Hmm.  Sounds very tempting.   I think Mark would like to go too (if his car is back together).    What is the approximate cost of a session?

[gr8kornholio]

I'd be in.  They have an engine dyno so don't necessarily need it back in the car.  Would love to see what they could make that 1380 do.  :-\

[MiniDave]

We paid about $120 each for the dyno sessions....

Mark, the engine dyno is at another shop about 45 min from Prather Racing's dyno shop, and an entirely different company. Setting up an engine dyno day would be a whole 'nuther subject.

I don't have a dyno, just a little engine stand set up to run in a cam and such, but it's good for getting some baseline setup done.

[gr8kornholio]

Well bummer, unless....  Lol  no really though....  just bolt it in the subframe and bolt that to the shell.  Close enough to a car right?....

[94touring]

Having a wideband installed to get your needles picked out and air/fuel ahead of time will make a dyno day go quick and easy.  Then it's a matter of testing timing to see what the sweet spot is.  On my rx7 for example the only real need for the dyno is to see what power you're making.  All the tuning is done ahead of time.

[MiniDave]

I agree in general, but it's difficult to get good accurate readings when you're driving down the road....on the dyno you can hold a certain rpm/speed and load and watch what it does....harder to do that when dodging potholes and idiot drivers.

Not so bad out where Dan's shop is, out in the country.....

[94touring]

Yeah you have to do WOT tunes on a long straight road in the middle of nowhere. Daily cruising tweaks can be done anywhere.  The benefit of the mini is you'll do 80 or 90 tops.  In the rx7 a 4th gear pull to get a good reading puts me at 140mph.

[MiniDave]

That's the cool thing about the dyno, you can do long pulls and just hold a certain rpm/load if you need to, although he mostly just got it rolling at about 2K in 4th, then set it on the floor and ran to 5k or so. On John's Mini he went up to 6K.....

[BruceK]

Dave, please let me know as the fall approaches- I'd like to be part of it.