New Dyno Day at Prather Racing

Started by MiniDave, September 01, 2018, 08:29:35 PM

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Vikram

Awesome. I've been looking for a reliable dyno thread for Mini's for so long, and this is it. When Dave posts the stock 1275 graph it will be really interesting to see the comparison to Dan's motor.

Dan, I assume power loss through transmission is now your biggest restrictor? Straight cut gears next?!

94touring

More photos. 

Vikram, no straight cut gears for me.  I'm calling it good as is.  You asked in my build thread about the flywheel and I think the difference was seen on the dyno during pulls.  My car was much quicker in the rev range, though the extra horsepower is probably a factor.  I let a few of the guys drive it and no one commented on clutch/flywheel difficulties. It's really easy to engage and drive.  Torque steer however...


94touring

#77
...

MiniDave

It was interesting to see the mixture ratios on the graph against the load.....that's where you really find the edge in performance. In my case mine was lean as it climbed the RPM scale, so we went with a little bit richer needle and while the overall HP only improved a bit (about 2 hp) the drivability definitely was better on the drive home - exactly where it showed me lean before. The engine just seemed to run easier on the highway.

Thanks to everyone for making the effort to come to the dyno day. All in all a great day yesterday.

Bruce and Michael Playle are driving home in the rain today - safe travels to you two!
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

The dyno makes it easy to spot the problems.  Well worth the money.  Also just fun having a number and graph to know is yours.  I'd like to clean up my bottom end once I find the right needles and see how much it improves the chart.

MiniDave

#80
Lets see if this will post.....

OK, a few things to note here, the power builds very smoothly, no jagged bumps, just a smooth straight line, next, the torque curve is very flat (not like you can do with FI of course) everything peaks at just about 5K rpm, as compared to Dan's chart, where the torque and HP continue to go up with the RPMs. This shows the difference in both cam profiles and cylinder head flow. The engine in my car is built for limited use, basically driving from 0 -65 mph, with the focus on mid range torque for easy drivability in town and high fuel mileage. The engine in Dan's car will do that as well, but has way more upside potential for speed....I'll be curious to see what kind of fuel mileage he gets.

Looking at the line across the bottom of the chart, it's a little bit rich at lower RPMs and a little bit lean at higher RPM, but it's all close enough for a street engine. Compare that to Dan's, he has a significant dip n the middle with a consequent dip in power and torque in the mid range. It's difficult to feel it but I'm sure with enough miles behind the wheel it will become apparent.....he's also way rich at idle and low speed where you really don't need it. The results of that are evident in the bumps in power at lower RPMs, once it gets past that point it smooths out nicely all the way to the top.

Unfortunately we didn't have any appropriate needles to change that, but some timing changes and dropping one jet and raising the other evened it out quite a bit and took the raggedness out that we saw in the early runs.

Edit by Dan: added my chart for side by side comparison.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

I almost wonder if changing dash pot oil would help that dip.  Seems like it comes on strong and right at 13:1 on the target line, then catches it's breath and dips slightly rich, then right back to 13:1. 

MiniDave

#82
I would try that, it might smooth out that little bit of raggedness at the top too?

I use 20W50 in my dashpots
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

#83
I know Calver says use 20w synthetic on anything modified intake or exhaust to reduce modulation in the carbs.  Atf and SU oil are best for stock.   Once the wideband gets in I'll start playing with oil to see if it calms it down.  Comparing the 2k-3k range to yours, if I can get my air fuel out of 10s and closer to 13 I should pick up a ton down there. 

Edit: ragged at the end if it's like my rotary tuning knowledge and dyno time, is ignition related, since fuel is essentially perfect there.  I was looking at that yesterday and thinking since I side gapped my plugs and gapped 30, I may need to bring them down to 25.  The side gap info says they should be gapped less than a standard plug.  So for example if you'd normally gap 35, take it down to 25.  On my rx7 you get ignition breakup when you start making big power without more spark, which I solved with an ignition amp, and flamethrower/csi dizzy on the mini.  BUT adding water and lots of it along with tons of boost begins to flood the spark and ignition brrakup comes back.  So you gap the plugs a bit tighter and it goes away.  I can't run standard rotary plugs for this reason and run a race ngk plug that I can gap. 

BruceK

I just got home - about 9 hours behind the wheel today. Michael and I hit a lot rain on the first two hours, then it was overcast with damp roads the next several hours.  By the time we went through Tulsa it was clearing up, so the last 4 hours were dry.   But Michael has another 5 hours or so tomorrow before he gets home.   
1988 Austin Mini
2002 MINI Cooper S
1992 Toyota LiteAce (JDM)
1997 Jeep Wrangler Sahara

MPlayle

Settled into a room at a hotel in Plano for the night and have been catching up on the email backlog.

For comparison: the basically stock 998 in the Moke posted numbers of 30.91 hp and 43.34 torque.  The only recommendation for the Moke was a very slightly richer needle as the AF graph was reasonably flat at about 14 all the way across - the target being 13.

(Note: A reminder to all - everyone's numbers are "at the wheels", so the Moke was putting out about right for a stock 998 that was factory rated 40-45 hp "at the crank".)

The other side note: the Moke set the shop's new record for lowest numbers.

MiniDave

Someone had to do it!   ;D

I think I was second lowest, so ......

In fact, I was so impressed with how tractable and easy to drive Dan's engine was I'm thinking of building one for my green car....of course it won't take me two years to get it built!   77.gif

How much was that cylinder head again?
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

#87
Mmm after the exchange rate I want to say $1200.  Maybe that included the rockers.  I will go through receipts and let you know.

Edit: $1260 with head and rockers. 

MiniDave

Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

Shipping was extra.  No core exchange due to shipping, plus I wanted the old head.

94touring

#90
Price guide:

1275 +40 with 10:3:1 slipper pistons. $265
Kent 266 cam    $315
KC super sport stage 3 head and 1.4 rockers   $1260
Maniflow stage 2 headers.   $110
Rc 40 twin box exhaust. $75
Maniflow twin carb fancy intake manifold  $170
Hs4 twin carbs with long ram pipes. $950
Csi 16 point electric dizzy on curve 7.  $285
Flame thrower coil  $50
Lightest verto flywheel available from MED. $145
Turbo clutch and 190mm plate vs the 180mm the kit has.  $145
------------------------
$3770


Then of course bearings, gaskets, cross pin diff, this, that... 

MiniDave

plus assorted seals, bearings, pushrods, alternator and gaskets...you also bought the Vernier timing gear.... and machine work to bore, hone and deck the block, plus two dips in the tank and having the crank machined. Plus someone competent to put it all together
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

BruceK

And Dan's engine made more power than the various MiniMania-built (and Seven-built?)  performance engines and probably ended up costing less.
1988 Austin Mini
2002 MINI Cooper S
1992 Toyota LiteAce (JDM)
1997 Jeep Wrangler Sahara

94touring

I was thinking that Bruce but didn't want to say it lol.  I do have plenty of work to do in exchange for Dave's services. 

Yeah I had to stop adding up cost.  I don't want to add in suspension to the total bill.  These wheels were about 1k after it was all said and done. 

MiniDave

#94
Almost all the HP in one of these engines is found in improvements to the head.....of course you need the higher compression, cam, ignition, exhaust and carburetion to make it all work.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

Quote from: MiniDave on October 07, 2018, 12:28:20 PM
Almost all the HP in one of these engines is found in improvements to the head.....of course you need the higher compression, cam, ignition, exhaust and carburetion to make it all work.

You should start advertising engines built to spec with the dyno sheet posted in the ad. 

Yep all the extra little things make the whole package.  The twin carbs were overkill since they don't provide more power per say, but should give better response and low end performance.  Ironically I'm rich there and doing the opposite of that at the moment.

gr8kornholio

That's where mine would have been an interesting comparison since it is one of those god awful expensive 7 ent. 1380 motors.  Paid for by the previous owner thank goodness.
I am the GR8KORNHOLIO! Are you threatening me?

Saussie Aussie 1965 Australian MK1 Mini.
"Beavis" - 07 MY/MY MCS, B/MY Konig Daylites, JCW sideskirts, TSW springs, TSW lower rear control arms -- Exploring the country with new friends since 11/09.

BruceK

#97
Found this site that converts horsepower at the wheel to horsepower at the crank.  Of course it's not exact, but interesting.   My car comes out at 70hp at the crank.

https://www.mk5cortinaestate.co.uk/calculator4.php
1988 Austin Mini
2002 MINI Cooper S
1992 Toyota LiteAce (JDM)
1997 Jeep Wrangler Sahara

MiniDave

Cool, it says my 52.5 at the wheels is 69 at the crank, more than I expected.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

#99
I hit an even 1 hundo.   

Here's a site I've used in the past as well.  Also showing about the same.  Here's a pic of the current day dyno conditions to plug into his formula.

https://robrobinette.com/Dyno_Correction_Calculator.htm