10 replies to this topic

[macaldron]

Hi everyone! Been really enjoying driving the mini around this summer, and had a chance to have it on the dyno yesterday. Chart is attached, figures are at the wheels. Very well satisfied with the performance up to about 4k RPM, and then...well, it must be related to me as it seems it has asthma!

Here's the spec:
1330 block, about 1700 miles since rebuild
Compression spec'd at 10.5:1
Head: JonSpeedRacing 12g940 with 35.5 / 29 mm valves (came with short block package)
Cam: SW5
Intake manifold: Minispares
Carb: hif44, BCE needle
Air intake: round airbox with K&N round filter with 4 1" holes drilled
Dizzy: fast road electronic (similar to Aldon yellow)
Exhaust manifold: Freeflow
Exhaust: RC40 twin box
Rockers: 1.3 ratio minisport

Fuel ratio also shown on chart - operator (experienced, but not with mini specific knowledge) said mixture looked really good.

I'd expect the peak torque to occur closer to 5k rpm, and the HP curve to climb to 5500 rpm or so on an A+ series, right?

Is the drop of in torque / HP over 4k due to head limits? Exhaust restriction from freeflow manifold, other?

Attached Files

•  Dyno - 20190817 (2).jpg   44.72K   17 downloads

Edited by macaldron, 18 August 2019 - 10:29 PM.

[unburntfuelinthemorning]

I'd expect to see more power from a standard 1275.

 

Was the cam timing set accurately?

 

How have you set the ignition timing?

[johnv]

Agree.. I'd like to have seen 75-80 from that

[macaldron]

Cam was timed in according to swiftune specs and alled for new duplex chain stretch. ign timing was set to top out at 32 at 4000k rpm. I agree Is expect it to make about 80 bhp at the fly. That would be about 67 at the wherls ...so I'm down about 10 up at the top end. However...at 4k rpm everything seems to be in good shape since its making about 81 lbft of torque at the fly.

[ACDodd]

If you remove the cork of an airfilter it will go much better. You will also need a needle change.

Ac

[macaldron]

Thx AC.  I have access to 1 3/4" K&N cone I can fit.  Any suggestions on the needle?  I will not have access to a RR operator who will be able to dial that in. Any suggestion based on experience would be incredibly helpful.  Thank you!

[Magneto]

I'm also surprised at those numbers and they do seem to indicate restricted air flow, given the sizes of the valves and such. I always thought the round stock filter boxes were as good as anything - certainly a lot quieter! But if that's the problem the butt dyno should let you know, you'll feel it continue to pull past the 4K rpm slowdown you now have.

 

I would sure like to see another pull on the dyno with the K&N to see what happens....

Edited by Magneto, 19 August 2019 - 05:52 PM.

[macaldron]

I'd love to do that (re-test with the K&N)...it's only time and $, right? :)

[ACDodd]

BCF I would thought with a RED spring, however it is very likely going to need custom machining to get it right.

Ac

Edited by ACDodd, 19 August 2019 - 09:34 PM.

[Earwax]

In regard dizzy curve, have you actually checked it stops advancing at 4000 rpm?   I have seen a well branded dizzy keep going to about 40 degrees straight out of the box. ( 20 degree dizzy cam with welds not set) Hope you get it sorted... should be a nice well balanced build.

[macaldron]

Thx AC - yes, I'd expect it would need massaging to really get it right.  Would just like to corral another 10 or so hp at the top end.  And thanks Earwax - good call on the dizzy.  I'll check it.