Mi16 Rolling Road Issue

[craig_007 1]

Had my 1900 mi16 on the rollers today to see what power it was making.

 

To my disgust it is only making 120 bhp at the fly and 90 at wheels.

 

I set the fuelling myself a few weeks ago with my wide band (the car is on carbs) and the figures for the afr are spot on for the power it is making.

 

It's got a H&H dizzy so there should be no issue there.

 

The only other thing I tampered with during the rebuild was the cam timing,Could this cause the power to be so far down. (I'm sure I set it to 1.5mm lift at tdc for inlet and exhaust)

 

The compression across all 4 are 220psi so there is no problem there.

 

Anyone else have an idea to what could be causing the lack of power.

 

I'm going to try and get a dti gauge tomorrow and check the cam lift.

 

Cheers guys

[Anthony 1,003]

Cam timing being out could easily cause it to be well down on power, as could the dizzy if it's nowhere near advanced enough - did you try swinging the timing to see if it improved things at all?

 

90hp at the wheels would certainly explain your other topic with it being slow at top end...

[welshpug 1,657]

what was the torque and fuelling like?

 

any printouts to see how it's behaving?

[craig_007 1]

It was 100lb torque it was making,It was also making max power at 6700 revs.

 

Fuelling was really good I thought,4th gear the run was done in,4th gear from 3000rpm wot the afr was 11, As soon as it got up to 4500 revs the fuelling sat at 13 on the gauge.

 

I did swing the dizzy(advanced it) and power dropped to 112bhp

 

I do have a printout but unsure how to get it on here.(it doesn't show AFR though)

Edited June 11, 2010 by craig_007

[boldy205 75]

Not slagging off H&H off atall, never delt with them myself, but have heard good things abouut them, but never overlook the 'brand new perfect part'.

[Baz 421]

The fact that it has a dizzy at all would be worrying me, and could may be a limiting factor.

[woodsy 0]

I would reckon check cam timing again as that power is well below what should be making.Did the guy at the RR set the carbs up or was it just a power run as the carbs could be way out aswell.I got my mi on carbs and dizzy with inlet cam and always makes around 173 bhp @ wheels on SBC rollers so yours should be way higher than what it is.When i fitted my inlet cam i balanced my carbs and set them up best i could without a co meter and made 100bhp on the rollers then got them setup properly and ignition timing and found all the lost ponies

[Baz 421]

That sort of power claim is fine, but SBC's rollers are optimistic at best, so just to throw the cat amonst the pigeons, i wouldn't be surprised if it's actually only about standard Mi power.

 

You're always going to be limited with a dizzy/8v ignition.

[woodsy 0]

I know mate i was thinking of going down the mappable ignition route at some point when funds allow, but for now its damn quick enough for what i use it for

[craig_007 1]

It was just a power run or lack of power run more like !

 

I've got a wideband lambda sensor installed and the fuelling at top is near spot on,If fuelling was the issue I assume it would show up as either rich/lean on the gauge,Flat out in 4th gear the AFR is 13.5 - 1.

[craig_007 1]

Another query I have regarding cam timing.

 

I read this, set the cam timing to 0.065 lift at tdc is a good starting point(This was what mine was set too) I set mine to this and my max valve lift is at 125 degrees after tdc(I'm led to believe max valve lift should be about 106 after tdc),Now to get the max valve lift down to 106 degrees after tdc the lift at tdc is going to be good bit more than 0.065.

 

My main problem here is my cams are unknown so the cam timing is a bit hit and miss.

 

All figures I'm talikng about are for inlet only.

[petert 586]

There is no way that 0.065" can equal 125 LCL. Physically impossible. More like 109-110. You need to verify your cam timing. There's nothing with a dizzy. Why not try standard 4 and 2 pulleys?

[fast_eddie 0]

Wait a min my 16v on 45's and 8v ignition( I swapped the engine myself ) and a halfords dizzy cap made and still makes very very good power and was used for probably 30k with no drop off? Standard cams, pulleys and timing.

[craig_007 1]

Hi guys,

 

Thanks for the input.

 

I do believe I made a mistake reading the DTI gauge !!

 

I thought each increment was actually 0.010 but it's not,So when I set the cam timing up to 0.065 it was really actually only set to approx .5mm of lift hence the reason it was so retarded.

 

Peter,Yep your spot on, I couldn't get my head around this yesterday but it eventually sunk in late last night what I had been doing wrong.

 

I'm going to redo the cam timing today,I'll set the inlet to 106 degrees and exhaust to 110 degrees and hopefully then I'll find the missing power.

 

It would appear that I have had it very much retrded though !!

 

If it I did actually have the standard 4 & 2 pulley I would have just went with them but the car has some kind of vernier pulleys fitted.

 

Again thanks for the input

[petert 586]

It's very hard to use the lobe centre method when the engine is in the car due to the dwell of the lobe at full lift. Unless you establish it by taking a measurement either side and splitting the difference. I'd just set both cams at 0.065" at TDC and go from there.

[craig_007 1]

Ok will do peter,Thanks for that.

 

I assume 0.065 is a good figure for the MI set up ?

 

Is the exhaust cam timing better suited to 0.065 ?

 

I'm sure I've got that around 0.040 just now but it's not a problem to re adjust.

 

Thanks again

 

Craig

[petert 586]

If standard cams, then 0.045" ish. I thought they were some type of after market cam?

[craig_007 1]

Apparantly they are,They were fitted to the car when I bought it (they still have 9mm lift approx)

 

The car also has some sort of steel verneir pulley(Like what can be found on some Peugeots I believe) So I would assume there would be sort of after market cams in there !

 

If I go to far with the cam timing I.E 1.8mm lift at tdc (Inlet) will that cause power to drop off also ?

[craig_007 1]

Here is the rolling road graph.

 

[craig_007 1]

Altered the cam timing today and the difference is like night and day.

 

When I was measuring cam lift today my dti gauge run out of travel at 10mm but the cam still had some lift left on it,Is standard cam lift 9mm ?

[craig_007 1]

Here is my new rr print out after cam timing adjustment and ignition retarded back to 10 degree static.

 

Does the graph look normal for an MI.

 

[welshpug 1,657]

looks about right for a 1.9 MI16 though I'd expect more than a 5 bhp gain from ITB's

[craig_007 1]

It's just on bike carbs.

[welshpug 1,657]

ah, that probably explains it then!

[craig_007 1]

Just got one more quick qestions guys.

 

I was back round at the garge with rollers today and we were both saying that ideally we would be looking for a little more power and the subject came back to cam timing again !!

 

After all the p3ssing about I've had with getting it going right I ended up setting the cam timing up to the same as a no2 pulley exhaust and 4 pulley inlet,Now if I don't have enough advance on the cam timing would that make a significant difference to the bhp/torque and is that noticable on the graph above.(Cam settings 1.4mm inlet/1mm exhaust)

 

I still have no idea on what cams are fitted but there is definately more than 10mm lift on both inlet/exhaust.

 

Am I correct in saying that standard has 9mm lift ?