B125AHM

[mercman]

Yes adding a washer under the spring will increase the tension on the valve which in turn will require a higher boost pressure to lift it.

If your'e not happy with the performance I would consider other engine mods rather than just raising the boost pressure, Iv'e seen an engine that blew up owing to being overboosted and not only is it not a pretty sight but it was a very expensive repair.

Lotus R & D decided on 0.5 bar for a reason.

Les

[ralphw]

Simon

Lets turn the issue on its head, what do you think the boost should be / overboost was. See if it is possible to get some info on the engine spec you have against what is needed, then assess the risk. There is always a risk. Every time the engine does one revolution it is being damaged. Based upon this damage model the engine has a design life. The damage is increased with load and speed, therefore if you are always driving the car at peak speed and load, you will probably cause damage at a much faster rate than if you were doing 70 down the A11. If you increase the boost then you increase the power and the load on the engine and potentially contribute to more engine damage. However if the proportion of the time you spend at that higher load and speed is very small as a proportion of the time the vehicle is being used then the increased damage incurred will be proportionately quite low and may actually be less than the duty cycle applied to the design to assess the design life.

Please note that this statement also assumes that commonsense applies and instead of 0.5bar you try to dial in 2.0bar. Please avoid this temptation. There is always a sensible limit to all modification based on the ability of the engine design to take the increase and the condition of the engine you apply the increase to. If a sensible increase is applied and it is used sensibly and not abused, then you will probably have no major issues.

Cheers

Ralph

[simonf]

Wise words Ralph!

I have dropped a 2.75mm washer in the base of the wastegate, i am not sure how much of an increase this has made yet, because i haven't had the chance to test it, my goal is 0.75bar as my car performed very nicely at this level before all of my woes began!

I haven't got the foggiest where to check for the data on whether this is going to put too much stress on my engine, has anyone had any experience in this field?

anyone running 0.75bar on a standard engine?

Whats the worse case synario? holes in pistons or blown head gaskets? if gasket would a thicker gasket reduce the compression and thus lower the risk.

As i do less than 3000mile per year, if the increase wear is minimal i would take the risk for the increase drive-ability!

Cheers

Simonf

[molemot]

When I posted a similar idea for increasing boost, one of the replies said that the LC turbo engine had a cooling issue. Increased boost = increased heatflow and there might be a problem with dissipating it; also the coolant flow through the head was less efficient than the later motors and could cause gasket problems and "hot spots". In the end, I didn't continue with the idea, which involved adding a platform under the wastegate spring, adjustable by a bolt threaded through the hole in the bottom of the wastegate...plus another hole drilled to vent the sealed chamber thus created. I did get the cooling mod. kit from the Lotus sale and fitted that, which has made the cooling system much better.

[mercman]

The amount of miles you do per year have nothing to do with it, it's how you drive it. it's a lot harder on the engine If you drive on full boost all the time rather than driving normally with an occasional blast

The engine I saw had literally exploded, the cyl head was cracked, a couple of the pistons had disintigrated , a con rod came through the side of the block and the crank had snapped at one of the big end journals.

Les

[simonf]

You are not wrong there buddsy and it would probably get delivered to you anyhow - thats the way steve usually works!!!

Thing is though i think 7psi equates to 0.5bar (to quote mercman) and that just isn't quick enough! I take on board les' comments on wrecked engines but i am only looking to increase by 0.25 bar which is only approx 3psi! I am hardly going ballistic and boosting at 2bar!

I am going to give her a run tonight an see what the results are, if they are disapointing i will rethink!

[simonf]

I have just taken the car down the road, and although the boost gauge was still reading 0.5bar it is quite apparent that the boost has been up'd! At least now when i put my food down it feels like it has a turbo! Got MY arse nipping up!!

[ralphw]

Simon

Firstly I would get your guage checked. Either the effect of the washer is substantial (you got the kick in the back you craved) and your gauge is stuck, or it is in the mind and therefore makes no difference or, something else is happening you havent figured it out yet. I would be surprised if the boost wasn't higher but I have no idea by how much. Don't give the car to much grief until you understand the situation a little better.

With regard to boost of about 0.75bar, that sits in between the early Stevens Turbo circa 1987 delivering 0.67bar boost with no intercooler or additional exhaust valve cooling and the SE turbo 0.87bar, intercooler and revised pistons, nickasil liners and sodium cooled exhaust valves. I think at 0.75bar you are probably pushing it a bit and I would suggest you aim for the 0.67bar as it seems consistent with your engine type. You might get away with 0.7bar if you are using the car for short squirts but any prolonged speed and load will probably lead to cooling problems especially around the top of the piston and the exhaust valves. In addition, as your car is carburettor, do you know what effect the extra boost will have on the mixture. If it goes rich it will assist slightly but if it goes weak then you are likely to accelerate the effects of overheating, especially in the area of the piston crown.

Cheers

Ralph

[AJay]

If your boost is noticably higher but the gauge still shows .5 bar then suspect a leak in the boost line to the gauge. I run .75 bar and when i had a leak in this line i only got .5 on the gauge.

My engine is far from standard the standard boost for your engine should not be any more than .6bar (8psi).

to achievd a reliable .75bar i have fitted SE piston and liners, a chargecooler, rejetted the carbs, improved the cooling through the head, fitted a triple core radiator, fully mapable ignition system and colder spark plugs.

You would probably see about 10 bhp per 1psi increase more with chargecooling (I am sure that there will be loads that disagree).

If you realy want to increase the boost you must look at the timing, Lotus technical recomend no more than 20 degrees dropping back to 19 at max torque.

Hope this helps.

[simonf]

You can now all say collectively......

we told you so!

On the Autum AEG run i was getting alot of crankcase pressure, enough to blow my dipstick out and coat my engine bay with oil, the car got progressively worse during the day (although in my defence - i didn't go balls out with the turbo!) when i got back to norwich andyclements and i started to look at the problem, we did a leak down test and found that cylinder 1 and cylinder 4 had very poor readings (about 80% in one and a stupid 90% in the other!) this could be holes in the pistons as you guys have suggested or it could be valves! as one of the clearances on cylinder 1 was almost non-existant i am leaning towards the latter.

[andydclements]

I think it will be open-engine surgery to find out all the issues.

Andy

[AJay]

whoops, sorry to hear that, but it happened to me twice before i realised why....... detonation destroying the pistons in my case, hence all the mods.

The LC engine is right on the limit with standard boost, if you have to rebuild and still want all the performance then i am afraid you will have to upgrade if its going to last more than 5 minutes.

Fingers crossed its only a valve or two.

[ralphw]

Simon

Sorry to hear, hope it is the valve, but I would also suspect the rings. I have had seen a few Sigmas lately with destroyed top rings. In this case however they would appear to be the product of some little oichs thinking they were putting on a high capacity coil when in reality they were not. End result detonation and F****d top ring.

Guess head is coming of. before you do however, try a wet compression test, if it makes a big difference it is the rings, if not it is the pistons or valves. If pistons or valves, please check your turbo for debris.

Best of Luck

Ralph

[molemot]

Desperate news, mate...out she comes again, then! A nice little winter's task; get it all fettled by spring when the sun warms the tarmac and the juices rise again!!

[simonf]

Cheers Buddsy, Guess i may be after a little more help from you soon

[simonf]

Just a quick update to say that andyclements came round last night with his super-dooper fibre optic endoscope, we had a little peek down the spark plug holes and we couldn't see any holes! Although we can't be certain until the head comes off - this looks like it might be the first bit of good news i have had for a while!!

We also ran a staight forward compression test and this test concluded that the leak down pressure test was accurate in fact it suggested that there was no compression at all in cylinder 1

[rogerch]

Come on stop slacking back to work, I need updates, you're my guinea pig, I was looking to go 1.2 BAR, maybe not?

Roger

[simonf]

Come on stop slacking back to work, I need updates, you're my guinea pig, I was looking to go 1.2 BAR, maybe not?

Roger

1.2 BAR!

Not without pistons fordged in the belly of hell and smelt by the devil himself you don't!

Just out of curiosity, what sized washer were you going to put in your wastegate to achieve this pressure

I will be hopefully taking the head off this weekend, barring any last minute jobs from the wife!

[rogerch]

Yeah I know what you mean even with the waste gate wired shut I haven't seen more than 0.8 on the gauge, but at the time I was thinking "this is quite quick"!!!

[andydclements]

How's the strip down going?

I've not heard anything about it from you, but I've been so busy I keep forgetting to call and offer assistance.

Andy

[simonf]

I know this thread has been dormant for a while, i have been slacking, but in my defence i have had new born baby duties to attend to and sleep deprivation!

Anyhoo, andy clements came round yesterday to help me get the head off! I had done a lot of the stripping out in preperation so all we had to do when any go there was undo the cam belt, remove the cam towers and oh yeah remove the alternator (again!!-must be the tenth time we have had to remove it in the past few months!!)

I had left the turbo and manifolds on as they were difficult to get to, andy decided that he didn't need a hoist and removed the head, the carbs, the turbo, the exhaust manifold, the wastegate and the wastegate manifold all together, by himself! If you werent impressed by him removing the gearbox un-assisted then you must be impressed by this feit of human strength! I am going to call him the human crane in future!

Once we removed the head, i thought for a minute that i was in luck as all four cylinders were full of water! but on closer inspection we did find holes in the pistons right at the top and right at the edge of the piston!

New pistons and liners for me then!

I will keep you posted of any further developments

[molemot]

Make sure you check the piston clearances.....!!

[Newts]

Well Si

I knew you'd had problems, but after reading this thread start to finish I was loosing the will to live, god knows how I'd feel if it was my car, think I'd have given in by now and bought another one !

Are you going to rebuild or replace with something else - V6, V8, modern turbo, reckon the engine out of your S3 would be quite usefull !

[ralphw]

Simonf

I guess you will be telling me more at the next meet. I can put my positive head on now. See if you can get some pics of the damage, will be interesting to have a look.

Wonder who mentioned burnt pistons

Cheers

Ralph

[simonf]

Simonf

I guess you will be telling me more at the next meet. I can put my positive head on now. See if you can get some pics of the damage, will be interesting to have a look.

Wonder who mentioned burnt pistons

Cheers

Ralph

I will take some photos when i get a minute and will post them on the thread

With regards "wonder who mentioned burnt pistons" Andy will tell you how much i was willing you to be wrong!!! But in my heart, i knew from the start that it was most likely to be the correct diagnosis!

I have to remain possitive at all times ralph, otherwise i was very likely to make a bonfire of her and buy something german and we just couldn't have that could we!

Well Si

I knew you'd had problems, but after reading this thread start to finish I was loosing the will to live, god knows how I'd feel if it was my car, think I'd have given in by now and bought another one !

Are you going to rebuild or replace with something else - V6, V8, modern turbo, reckon the engine out of your S3 would be quite usefull !

I know what you mean Colin,

I am not a lucky man

I find the best way of dealing with it all is just to keep focussed on the positives, like, erm, I can't remember what the positives are any more

I am just going to soldier on with reconditioning my engine with new pistons, liners and new shells! I don't trust my luck anymore so i will probably be fitting a new oil pump!!

Probably won't be on the road this summer but we will have to wait and see.