Mi16's Die And S16's Don't...

[Tom Fenton 1,525]

That is the bit that I don't understand, the fact that "some" Mi's will take it all day long, and others will spin shells at the first hint of a corner.

My track car has done 8 years of trackdays on pretty much any tyre you care to name from Toyo road poxies to full slicks. Engine has not been apart other than a head gasket replacement to cure it weeping coolant from the front of the block/head joint.

Yes it is now very tired and low on compression and needs to come apart, but it certainly has no issues with oil starvation, as if it did there would be either a nasty knocking noise coming from inside it or a large hole in the front and rear of the block by now.

[Mad Scientist 106]

Could the fact some survive better than others be down to bearing tolerance?

[Carbs4me 45]

Probly totaly unrelated but My 1.9 8v spun a shell on rod 2 3 times after a rebuild... after that i pretty much threw the engine into a corner of the garage and never gone back to it. i put it down to the Shell been incorrect sizes from standard due to ware obvisously! so it could be an shell issue itself! if there not exact there probly wearing away massively from the second you put it together.

 

Each rebuild lasted me 4 month thats with a good service... and it actually spun its 2nd set of shells on tick over and it lodged itselfs with the other shell on the rod.. it was always the bottom shell on the rod too that went.

[petert 551]

I ran my engine for over 3 years on semi-slicks and never had a whiff of oil starvation.

 

Depends on how well you drive it!

 

Heat also speeds up the process. Hot thin oil isn't particularly useful. The more you can do to keep the oil cooler, also the better. ie cooler, increased capacity etc.

[wicked 103 3 Cars]

Nobody seems to have mentioned fitting a GTi6 head to the Mi16.

 

 

In my first post

 

 

The issue has been addressed by Peugeot with new design of the RFS and XU7J4 heads. On the EW engines, the drains are even bigger and put on the back side of the engine (Look at Sandy's topic about the EW's).

[Tom Fenton 1,525]

Probly totaly unrelated but My 1.9 8v spun a shell on rod 2 3 times after a rebuild... after that i pretty much threw the engine into a corner of the garage and never gone back to it. i put it down to the Shell been incorrect sizes from standard due to ware obvisously! so it could be an shell issue itself! if there not exact there probly wearing away massively from the second you put it together.

 

Each rebuild lasted me 4 month thats with a good service... and it actually spun its 2nd set of shells on tick over and it lodged itselfs with the other shell on the rod.. it was always the bottom shell on the rod too that went.

 

So in your case clearly the rod itself was the problem, and needed to be resized or replaced. Not a bearing issue at all and sorry to say you threw good money after bad by not having the rod checked.

[Alan_M 66 1 Cars]

Could the fact some survive better than others be down to bearing tolerance?

 

What about the quality of the rebuild (bearing clearances etc)?

 

And, how many times the lights been on and/or how often its ran on low pressure. Once wear develops in the shells, surely it's downhill from here on.

[Cameron 16]

Depends on how well you drive it!

 

Well, without breaking my modest character too much.. The only cars coming past me on my last track outing were a couple of Caterhams on slicks, so I'd say it was at least driven to the point where most are experiencing oil starvation problems.

 

I think chasing bearing tolerances won't reap much reward for your efforts, you need to stop the oil pressure dropping in the first place. Oil temperature could play a part as Peter says, I was running a 16 row x 235mm cooler mounted in unobstructed flow, so this could well have helped.

[Normski 1]

I think the oil temperature is a factor in this. My Mi16 track car had no surge problems at all running on full slicks for three or four years. It had a single vertical sump baffle welded into the ali sump. I also got rid of the water heat exchanger and fitted a mocal air-oil cooler plus a new water radiator so that the temps were well under control.

My first time on track (with the stock engine) as soon as i'd done the conversion to my road car, I had surge and ran the bearings. This happened again after i had replaced them (I didn't know it was a common issue back then), so i then rebuilt the whole engine with the above extras and it was solved (multiple dropped valves are an other story).

[B1ack_Mi16 67]

Could the fact some survive better than others be down to bearing tolerance?

 

Regarding tolerances. Just something I picked up by my engine builder when he was grinding the crank on the 2.3 Mi16.

 

He told me he did grind it a few thousands extra, to get some extra clearance for the big end bearings. This was apparently to get more oil flow through the bearings/crank, and was done to get better cooling of the big ends. I guess cooler big ends means that the bearings are not as soft as if they were hotter, so that might also be an factor, as they would not totally collapse as easily.

 

Never had surge issues on that engine though, never seen the lamp come on, but I guess the mechanical lifters is doing some positive contribution.

[Razkin 0]

I don't think he meant the bearings itself, they should never come in contact with the crank, but if you have more oil flow, the (local) oil temp will be cooler and the oil film is less likely to shear.

[B1ack_Mi16 67]

It was the crank that was ground a tad more than the standard tolerances.

[Razkin 0]

Yes, I meant that it is not done to protect the bearing itself(cooler and thus harder), but to protect the oil film.

[unariciflocos 49 1 Cars]

Ok, the shell on my number two rod spun yesterday on a sprint up some hills, but at no point did I see any pressure drop, oil light came on at idle immediately after I heard the knock and pulled to the side, so it's working fine.

 

This is the 3rd crank and shell I loose so I phoned a guy that's been racing Mi16 205s for 7 years and has been leading the championship for pretty much the same time and he had a good laugh at me and told me he lost 3 engines the same way and that since then he has ground the crank 0.05 mm more than standard, used high quality shells, Motul 300V oil, no oil cooler, no 6 bar spring, only thing he does have is a baffle plate. So no issues in this configuration for 6 years on tarmac rallies and circuit racing on full slicks, wide track, rally suspension.

 

So just as B1ack_Mi16 said, it may just be the issue of increasing tolerances. My crank is at the machinist now, will grind it to 49.70 with 0.25 bearings and give it another go. If it doesn't work I'm setting the car on fire and buying a Honda.

[unariciflocos 49 1 Cars]

Just found out that bearings come in +0.3 mm so I'll have it reground at 49.65

[wicked 103 3 Cars]

...

and that since then he has ground the crank 0.05 mm more than standard, used high quality shells, Motul 300V oil, no oil cooler, no 6 bar spring, only thing he does have is a baffle plate. So no issues in this configuration for 6 years on tarmac rallies and circuit racing on full slicks, wide track, rally suspension.

 

 

Motul 300V 15W50 iso 10W40?

[unariciflocos 49 1 Cars]

Don't know, will ask and get back to you. I'd guess 15w50.

[C_W 3 1 Cars]

I used Castrol Magnatec 10/40 in mine, no problems for about 10years.

[Koos Agtereek 0]

I read Ties subject great interest.

 

I was also thinking that the oil starvation was caused by the head holding to much oil.

So I went the same path as Cameron, RFS(XU10j4RS) head with MI16 bottom end (D6C instead of DFW which Cameron has). The build included, fine crankshaft, new bearings, RFS oil pump with big chain wheel on the crankshaft, chain chard, baffled sump with trap door (no windage tray).

 

The engine was doing fine on the street, on the first track day it started smoking when hot and coming out of long right hand corners and on the strait revving it up over 6500 RPM, so I took it easy and sat the day out.

On the next track day I had an oil catch tank installed and the smoking was over (of course), so without the warning smoke signals I pushed it to the limits resulting in a hole in the Block by oil starvation.

 

I threw the MI16 aside an build up a Standard RFS. Cleaning the oil-ways through the crankshaft I noticed the difference between the MI16 and RFS cranks. After another track day with two MI16’s with sprung big end bearings I came to approximately the same idea as Wicked. But with some extra thoughts.

 

The viscosity of the oil is a important factor, when the oil is hot it will flow almost freely to the head because of the lack of resistance in the oil ways to the head.

In the oil ways through the little hole in the main bearing into the oil path in the upper main bearing half , into the spinning crank, over winning the centrifugal forces flowing to the centre of the crank then splitting the oil flow in two to bigend bearing 1 and 2, the viscosity will be a smaller factor.

 

It is probably getting difficult getting the right amount of oil to the two big end bearing.

 

That is of course why Peugeot changed al it’s cranks to a mean bearing feeding (1) bigend bearing.

 

So the balance between how much oil is going to the head and to the bearings is in my opinion shifting during heating (viscosity) up and revving up.

High rev’s, hot oil and corners on slick together...

Edited October 9, 2012 by Koos Agtereek

[cybernck 400 1 Cars]

So, what would happen with an Mi16 head on a RFS block, due to the changes in the crank design?

[wicked 103 3 Cars]

Crank design already changed on the S16, so you're building (kind of) S16 then...

[cybernck 400 1 Cars]

I meant 1.9 Mi16 head. Would it be too restrictive for RFS oil pump etc?

[Koos Agtereek 0]

I meant 1.9 Mi16 head. Would it be too restrictive for RFS oil pump etc?

 

Well in my opinion this would work, you might want to put a restrictor in the oilway to the head, i know someone who did this. The rfs is a better bootom end than the s16, you lose the the lower weight advantage of the mi 16 though. And this is for me the only reason for wanting an rf16 hydrid over an rfs.

[welshpug 1,622]

use 86mm crank in alloy block to make revvier 1.9? will be 1861cc.

 

what in the S16 bottom end is inferior to the gti6? given its the same crank+block?

[Koos Agtereek 0]

Firstly I would want to want to drill some extra holes in the 88mm original MI16 crank to get the oil flow more freely through the crank to the rod bearings like done on Porsche 928 cranks (see picture).

 

If I am correct a S16 has no windage tray. A 86 mm crank in the MI16 bottom end would be a good idea, you would need either custom pistons or rods or to deck the block to get the compression ratio sorted. Custon rods would would be nice to get the rod angle further improved to. What would custom rod's cost roughly?