Mi16 Conversion Finished..

[Guest johan 309gti16]

Hello,

 

When I was reading this interesting article, I could not complete understand if I can use a 8v crank (1.9 GTI) in my MI16, without make adjustments. A gay sad that I can use a 8v crank without any problems in my MI16. I this true?

 

Dues anyone have some drawings from a 8v and MI16 crank, with measurements.

 

Thaks for the infomation.

 

Greetings Johan

[nick 3]

The 8v crank fits in without modification. The only difference is that the Mi crank is counter weighted, but is a lot heavier.

 

Nick

[Guest johan 309gti16]

Thanks for the quick reply. That is a relieve that I can use a 8v in a MI16.

 

A lighter cranck means that you a lower torqeu?

 

Greetings

[nick 3]

I've not had it on a rolling road yet so can't say for certain.

 

In theory, yes, in practice I would say not. Mine pulls hard from about 2-2.5k, which is good bearing in mind that my downpipe doesn't have the split in it (which is supposed to lose torque as well)

 

Unbeknown to me my engine had the 8v crank in it when I bought it, I have a few friends who own Mi's and not one commented on it being harsher or more vibey than theres (all Mi cranked)

 

I personally can't see any downside to fitting an 8v crank unless you are going to use megga revs all the time.

 

Nick

[Guest johan 309gti16]

It's only road use. The cranck of MI16 are getting roar these day's, zo I have a spare 8v cranck in case off failure.

 

Has someone drawings of a 8v and 16v cranck.

 

Johan

[B1ack_Mi16 67]

Engine will not get less torque by changing to a lighter crank.

It will however loose some rotational inertia so it will be easier to stall it when setting off in 1'st gear.

 

(not that I think you will feel it in this case as the weight difference is not that big between the cranks anyway.)

Edited December 15, 2008 by B1ack_Mi16

[Guest johan 309gti16]

Have have 1 question jet. How is the balance (with the 8v crank in) from the engine in higher revs compared with the standard MI16 crank? Because the MI16 crank has 2 cheek’s while the 8v crank has 1.

 

Greetings Johan

[welshpug 1,661]

The pistons are machined to give the same little end/piston clearance as the 8v, so they are just crank located.

 

any idea how much wider the 8v rod was? or did you just do it till the rod fitted

[veloce200 3]

Interesting thread however if my 8v gets the gauge moving massively on the road I just don't see this working especial thought it was accepted its the crap pick up design that causes surge on 8v and 16v and the mi head just makes things worse?. I mean if the gti6 head works fine what's the point in mucking about with a crank designed for lower revs?

[nick 3]

The rod fitted (it was piston located in the first place) so it was just a matter of machining the pistons to give the same clearance as an 8v piston.

 

The whole point of doing it was to try and cure oil surge. Me and Martin have come at it from a different angle and, so far, I'm happy to say that it works... I haven't tracked it yet, but there were certain places on my drive to work where the gauge would definitly drop, it doesn't do this anymore.

 

I'm assuming that you haven't read the thread all the way through, as I didn't buy a 8v crank and rods to do this, my engine already had that crank in it so that is what we used, if there had been a Mi crank in there we would have used that instead. There is nothing wrong with the 8v crank in an Mi for a road car.

 

Me and Martin got a bit tired of being told on here what the "recognised" causes for the surge was, but no one seemed to be doing much to cure it, so we tried something different (the idea incidentally came from a very well respected tuner who built Martin's BTCC Mi engine and the engines for Peugeot back in the day...) With Martin owning his own engineering firm the cost to machine 4 pistons and buy 4 8v rods was minimal and if it didn't work.... I'd still have a nice fresh rebuilt Mi in my car.

 

Nick

Edited December 31, 2008 by nick

[veloce200 3]

I'm assuming that you haven't read the thread all the way through, as I didn't buy a 8v crank and rods to do this, my engine already had that crank in it so that is what we used, if there had been a Mi crank in there we would have used that instead. There is nothing wrong with the 8v crank in an Mi for a road car.

 

 

i did indeed read the entire thread. the reality is any wet sump engine on track on slicks is going to suffer some degree of oil starvation and regular shell swaps would be advisable. i understand the points made but surely if oil is pissing out where the crank and rod join thats more down to incorrect running clearance? i'm also struggling to understand how even if you improve on this area it makes a blind bit of difference when cornering as it's the movement of the oil away from the pickup and head drain that causes the problem is it not? i have zero experience of mi16 so i'm not being confrontational just trying to understand how this will help surge?

[nick 3]

I didn't mean to sound arsey with the last comment, it's just that all the info on why the 8v crank was used is in the thread.

Our idea was that the 8v surges just as bad as an Mi, but the 8v holds the pressure for longer in the galleries when it does. It's as though the Mi has a massive oil leak on the big ends. The oil pressure from cold is off the scale now and sits just below half way at hot idle, that extra pressure has come from the fact that the engine is oil tight internally.

 

It isn't incorrect running clearance, they are designed like that (piston located, with clearance on the crank and big end) the 8v is the opposite, with the big end a nice snug fit on the crank with the running clearance on the small end/piston.

 

It would be interesting to find a way of comparing an 8v and Mi on how long they hold pressure when starved of oil, like dropping the sump with them running and timing how long each one holds it's pressure.

 

Nick

[pugman211 0]

Fantastic read Nick, and great work from both you and martin. It will make rebuilding my engine that bit more interesting now as i dont know which option to use. Again, just looking at making a reliable engine, only difference being mine will never be on track...lol

[Cameron 16]

Me and Martin got a bit tired of being told on here what the "recognised" causes for the surge was, but no one seemed to be doing much to cure it.

 

GTI6 head.

[nick 3]

Is that what you have done Cameron? If so is it successful?

 

Nick

[Cameron 16]

Yep, 1.9 alloy block with a GTI6 head. I did it last year and not had any problems with surge on track. Makes very good power too.

Edited January 2, 2009 by Cameron

[nick 3]

So was this engine a "surger" to start with?

 

Nick

[Cameron 16]

Not massively.. had a few spots where the needle flickered on last year's ring trip. Took it out there again this year ('08) after all the work had been done (engine, SD roll cage and A032s) and not a hint of it, although my laps were cut short by a broken driveshaft.

Anywho, will be fitting some digital gauges this year and heading off to Germany again armed with a few more spares to see what's what.

[nick 3]

Sounds like an effective cure so far, which is whats been lacking..! I can't wait to get mine on track to see if it's cured once and for all, I know all the places at Donington that it was surging so should be able to see any difference straight away.

 

Nick

[Cameron 16]

Yeah will be interesting to see how well it works.

 

Are you going to be restricted on revs with the 8v crank, or isn't there much between them anyway?

[nick 3]

Just std Mi rev limit. According to Puma racing the rods are very strong, and he doesn't even mention the cranks strength so I'm assuming thats fine. I imagine all the 8v race engines are revving to 7500/8000 with no problems (never heard on here of a broken crank) plus it is 99% a road car, so it only ever sees the the rev limiter occasionally.

 

Nick