24 replies to this topic

[Raggedroy]

Help please.

I have recently fitted twin HS4’s on my 1380. I had it running ok but wanted to make sure I had the right needles and springs so I put it on a rolling road last week. It produced 118bhp (flywheel) after changing the springs and needles and seemed to perform well. On the drive home something felt odd i.e a slight misfiring or hunting feeling when the throttle is held stationary. Performance still seems fine when on power. Revving the engine when stationary produced a very lumpy sound like it is running on 3 cylinders. Since I have had it home I have changed the plug leads and checked compression (180 on all cylinders), checked rotor and and cap. Before the rolling road it had new NGK plugs (BP8ES), new rotor arm and new distributor cap. It’s not loosing water, I haven’t noticed water in the oil or running hot. I have swapped one plug at a time to try and identify a plug breaking down. It may or may not be related to the rolling road tune, any ideas where to look next?

Cheers

Engine Power 119.0 BHP Wheel Power 61.7 BHP Torque 95.4 lbf.ft

1380, MED AGSP 300 Duration Cam, Lightened and Balanced Con Rods, Omega Pistons Lightened Flywheel Ported Head 35x31 Valves, Aldon Distributer

Edited by Raggedroy, 01 May 2018 - 07:24 PM.

[nicklouse]

put some 6s in the 8s will be fouling.

[Raggedroy]

put some 6s in the 8s will be fouling.

It has had 8's in it for years as recommended by MED when they built the engine with no problems.

[nicklouse]

so what do they look like?

[Dusky]

Losing 60 bhp through the drivetrain? Thats a lot!

[Raggedroy]

so what do they look like?

I would say they look like its burning clean and look a nice grey colour.

[imack]

I've got a similar spec engine to you, running MED's FIA15 appendix k cam. Had it set up a couple of years ago by Peter Baldwin, I'd been running bp8es, he advised bp6es, recons he runs 6es in his miglia.
Have you checked the carbs? One jet stuck down, needle valves leaking, needles secure, dash pot oil/piston, sticking suction chamber, air leak, linkage, carbs picking up together?

[Raggedroy]

I've got a similar spec engine to you, running MED's FIA15 appendix k cam. Had it set up a couple of years ago by Peter Baldwin, I'd been running bp8es, he advised bp6es, recons he runs 6es in his miglia.
Have you checked the carbs? One jet stuck down, needle valves leaking, needles secure, dash pot oil/piston, sticking suction chamber, air leak, linkage, carbs picking up together?

I have checked the needles, oil, pistons operate/ pick up together, linkage. I haven't checked the jets. Cheers I will go and look.

[Raggedroy]

 

I've got a similar spec engine to you, running MED's FIA15 appendix k cam. Had it set up a couple of years ago by Peter Baldwin, I'd been running bp8es, he advised bp6es, recons he runs 6es in his miglia.
Have you checked the carbs? One jet stuck down, needle valves leaking, needles secure, dash pot oil/piston, sticking suction chamber, air leak, linkage, carbs picking up together?

I have checked the needles, oil, pistons operate/ pick up together, linkage. I haven't checked the jets. Cheers I will go and look.

 

Just checked dash pot oil, jets, linkage. I guess it could be an air leak.

[Turbo Phil]

How on earth are you losing nearly 60hp through the transmission ? I agree with the comments on the plugs, IMO 8's are far to cold and they are easily killed off if they get fouled.
I run 7's on my turbo @20+psi of boost with no issues, so I'd think 6's will be fine for you.

Phil.
 

[Raggedroy]

How on earth are you losing nearly 60hp through the transmission ? I agree with the comments on the plugs, IMO 8's are far to cold and they are easily killed off if they get fouled.
I run 7's on my turbo @20+psi of boost with no issues, so I'd think 6's will be fine for you.

Phil.
 

What do you loose through your drivetrain? 

[Earwax]

What timing did you end up with?.  Combination of plugs ( first choice) and advanced timing  .. ( good for power but may be too early for idle)?  300 degree cam is going to be lumpy, was it warm?,, again combination with plugs.  NGK 8s is more in keeping with a NA 'race' motor ( ie sits over 5000rpm all of its life).  Hope you get it sorted. Drive train loss for 120 at flywheel  ,,,maybe down to 85 -80 at the wheels

[minimans]

Bit OT but how do they calculate engine BHP from a wheel dyno? do they use an arbitrary percentage for drive train loss? and if so how do they calculate it?

[timmy850]

Bit OT but how do they calculate engine BHP from a wheel dyno? do they use an arbitrary percentage for drive train loss? and if so how do they calculate it?

They use some kind of correction factor. Hopefully a well established company was able to do back to back engine and chassis dyno runs and found a good correlation over different engines to calculate a meaningful factor...

 

Most people over here only care about what you've got at the wheels.

[nicklouse]

most modern Rolling roads can measure the resistance in the transmission.