Mi16 With 8 Valve Rods

[crf450 0 1 Cars]

As some of you may know Nick and myself rebuilt a badly surging Mi16 engine using 8 valve rods to try and combat pressure drop due to oil surge. The theory for this basically stacks up better than any other theory in my eyes including the theory that the Mi head holds oil.

Our theory was the Mi oil circuit struggles to keep pressured up because of the amount of oil that escapes around the 16 valve rod, you fit the 8valve rod and you plug that leak meaning the engine requires a lot less oil to keep pressure.

With this in mind we decided to rebuild Nicks engine which had just died in its first session on track using 8 valve rods, we also added a GTI6 trapdoor sump and windage tray.

After the build Nick reported back that on the roads he drove to work on he never saw the pressure gauge drop on corners that he knew it was dropping before and also on this 300degree corner on the inner ring road in Derby going as fast as he dare he again saw no drop when he'd be getting the oil light on before.

We always maintained that the best way to say for definite if we'd made a breakthrough would be to get the car on track on slicks with a good quality gauge fitted but we thought using the standard gauge that was showing surge before and was not showing any surge after was a good indication we'd change things for the better.

To cut a long story short Nick sold the car to one of our mates who turned it into a track car and on our advice fitted a proper pressure gauge. As soon as he went out with 888's the gauge started to show surge and the extent of the surge was confirmed at Spar when the motor spun a shell on a double apex of camber left hander.

Our theory hasn't worked.

Cheers Martin

[Anthony 1,003]

Damn, that's a shame as the idea looked hopeful for a while. Back to the drawing board then.

[GilesW 41]

I think the best thing about all this is that you guys tried something very plausable, and then were man enough to come back on with the bad news.

 

Top marks for trying, and top marks for giving the full - although dissapointing - story.

[Henry Yorke 269 3 Cars]

Cheers for the update Martin. I know you had been pondering this one for a while. It seem there is no cure for an ally Mi16 apart from dry sumping and anyone who tells you different is obviously not going fast enough!

[Baz 421]

Ohh! That's a bit of a sh!tter!!

[pug_ham 244 3 Cars]

Damn, that sucks.

 

At least you tried something that showed no reason why it wouldn't work but in practice now shows the problems lies elsewhere, maybe with the head holding oil.

 

DES did some internal work with regards to the return oilways or something afaik which Darren Halliwell & afaik Ade (PVFC pug) never had any problems with ssurge on DES built modified Mi engines.

 

Graham.

[stu8v 68 1 Cars]

RAT Developments fit an external return from the head to the sump to stop such issues.

 

Ill be copying my mates when he gets his built engine back.

 

AFAIK they dont suffer issues even with the cars they have run in competition.

[rallysteve 22]

Thats a real shame, but again well done for giving it a try.

 

Has anyone ever tried running an electric oil pump set up with a tank?

 

Steve

[James_m 0]

Thats a real shame, but again well done for giving it a try.

 

Has anyone ever tried running an electric oil pump set up with a tank?

 

Steve

Like an accusump? I remember someone did quite an in depth test with one of these a few years back, if I remember the conclusion was it was like shutting the stable door when the horse had already bolted... I.e it couldn't supply enough oil to combat the surge, and in a track situation where surge was happening Corner after corner it was just emptying the tank continously and not having the time to refill the tank.

 

Sad news it didn't work, dreaded left handers...

[Cameron 16]

As much as I'm a little relieved to have been right about this, I have nothing but respect for you two for trying this out and especially for admitting that it failed. It's good to see people trying something new.

Edited October 10, 2010 by Cameron

[petert 588]

Yes, well done. I don't think there's any one answer other than dry dumping. The more work you do the better the control will be. Even the best wet sump will have fluctuations in pressure, setting limitations in cornering based on tyre choice, chassis etc. Of course knowing where those limitations are is half the battle.

 

I'm going to build more engines with 8v rods, more so to control side thrust. None of the after market 83.50mm pistons I've used control the rod like the standard piston. I have to do considerable more work machining the inside of the piston vertical, then making thrust washers to centre the rod correctly. It's considerable less work to rebush an 8v rod.

Edited October 11, 2010 by petert

[JeffR 51]

Has anyone fitted 8v rods & solid lifters to the Mi head?

 

With less oil in the head to begin with, possibly the drains could cope better in getting the oil back to the sump & the leakage around the rods reduced (from std 16v ones).

Edited October 11, 2010 by JeffR

[Sandy 191]

We've never known any problems with our customer's solid lifter engines.

[JeffR 51]

Thanks Sandy. That's the direction I'm heading with my BV head.

 

Are any of your customers using them in track cars?

[brumster 135 1 Cars]

Can I just add a "clap clap" for trying and, more importantly, for coming back on here and informing us of the 'failure'. I often get involved in the surge debate, as you know, and have long since been a purveyor of a theory... it's very clear that there is some weird and wonderful 'attribute' to mi16's that escapes us all, that decides whether it's a surger or not

 

Bad news, but pat on the back all the same.

[Tom Fenton 1,542]

it's very clear that there is some weird and wonderful 'attribute' to mi16's that escapes us all, that decides whether it's a surger or not

 

Agree with this 100%- it just seems that some do and some do not.

 

Personally I've been lucky- an alloy Mi16 used for 6 years of trackdays on semi slicks and full slicks, with 2 different cylinder heads on it, and apart from getting a little tired now due to use and abuse, still shows good oil pressure.

[matthewm 1]

I rebuilt mine with 8v crank and rods a few months ago after speaking to Marin, as I felt this was the most logical reason I'd heared.

Didn't want to comment before as I'm not convinced the crank and rods I used were perfect, however I did still noticed the pressure drop when given stick on roundabouts with grippy tyres, although only down to 20psi on my aftermarket gauge.

So far used it on 2 Welsh championship road rallys, finishing top 5 on both so its had plenty of abuse and holding up well though.

 

I'm convinced the engine feels livelier with the lighter 8v internals (Anyone got any science to prove/disprove this??) and given the option I'd go with the 8v stuff again especially if I had them readily available.

[brumster 135 1 Cars]

Certainly the 8v crank will be lighter - it's got only half the webs - so what you say makes entire sense.

[welshpug 1,661]

I was always slightly curious as to why this was seen to be the answer as the 2.0 rods have much less side clearance on the crank, and they still suffer as much do they not?

 

RFY bottom end and RFS bottom end

 

 

Ade (PVFC pug) doesn't have surge issues as he's on a dry sump !

Edited October 11, 2010 by welshpug

[DrSarty 90 1 Cars]

Echoing the comments: well done for trying and reporting.

 

So - (dons firesuit) - why don't the iron block S16s (2.0 Mi16s) surge then? The head's practically identical albeit having an oil drain/feed hole for the vacuum pump. Could that be the reason?

[welshpug 1,661]

ohhh they do Rich they do!

 

its why my ZX doesn't run an RFY any more! long tight left hander, needle dropped right down, 20 miles later and it was rattling its tits off.

 

Mine was a very early 2.0 from 1992 and didn't have a windage tray.

 

RFS now installed.

Edited October 11, 2010 by welshpug

[Cameron 16]

My Mi16 / GTi6 engine hasn't had any surge yet.. it's managed 3 'ring trips and a day at Oulton Park so far, all on A048's.

 

I'd never go as far as to say it was surge proof, but it does seem to be holding up very well! Time will tell I suppose.

[welshpug 1,661]

If its a wet sump you will always get surge to an extent.

 

What you (Cameron) haven't seen as yet is the effects of starvation of the oil pump for any reason, and hence a low pressure reading, be it due no oil for the pump to pick up because its on the end of the sump, or half of it is still in the head for example.

[TT205 42]

Well done Martin and Nick

 

Bad news in the end but was well worth a try and did look as though you may have cracked it

 

Don't be down about it

 

Good on yer

[Baz 421]

If its a wet sump you will always get surge to an extent.

 

What you (Cameron) haven't seen as yet is the effects of starvation of the oil pump for any reason, and hence a low pressure reading, be it due no oil for the pump to pick up because its on the end of the sump, or half of it is still in the head for example.

 

Exactly, any wet sumped engine will 'surge', it really bugs me that people think this magical thing is only attributed to the 1.9 Mi16.

 

In fact, whilst on the subject, 'surge' itself is nothing to worry about, it's the resulting starvation that causes problems. I happen to strongly agree with this though...;

 

Agree with this 100%- it just seems that some do and some do not.