The '2 ton bugswatter' - back for a gentle stroke

[da_trem]

Since you don't have a/c anymore, are you still using the elec. auxiliary fan or only the thermostatic fan only for cooling that beast?

[JP]

A80Avant as PRJ rightly said the car is a development tool to try and discover issues that have not been touched upon before and find ways to resolve where possible. As there is two types of turbo use in the I5's it's those seeking peak figures and use their car for racing and there is those that want best of both worlds streetability and racing with as broad a power band as possible.

The first type racing is the easy one it's what most people pursue on a budget as the secondary requires a lot of modification to achieve a more modern drive to the vehicle. Well we achieved the secondary result with an amazing 4000rpm powerband which made it the most savage thing I'd personally driven on the road once WOT was achieved.
However it came at a cost which only came to light after PRJ had returned home. Unfortunatelly it took 3 cranks and rods to finally discover the issue. Purely down to the lack of datalogging ability when there is no one sat mapping next to you.

The car would do a big end bearing when short shifting at around 6200rpm on the road during overtaking manouvres. However be perfectly fine at WOT shifting at 8k.

First it was put down to oil starvation/old oil. So a fresh crank was thrown in and new oil and of we went again, car ran as it did before but once again the minute I short shifted at 5800rpm this time on an overtaking manouvre I heard the dreaded clack clack clack again.

Still thinking we had an oiling issue this time round with once again fresh crank rod and bearings I went for an oil with an anti shearing compound in it lterally preventing a bearing to ever contact the crank. This time round it still done the bearing but the car just carried on driving with no real resistance just a load of noise. Even did a couple of redline passes just to make sure it wasn't the twin plate clutch making a racket.

Unfortunately it wasn't the clutch. However upon pulling the engine apart for inspection we discovered something new. There was no damage to the crank journal and the blue'ing on the rod was barely noticeable and you could still see the honing marks in the caps. Instead no.5 sputter bearing had been crushed to 1.5 x it's original width and no.4 to 1.25x with the other rod bearings showing signs of pressure deformation. The anti shearing compound in the oil did it's job indicating that the failure was infact not related to oil starvation.
After consultation with several knowledgeable people we came to the conclusion that although the mods on the engine had allowed it to make power very early it was also the cause of it's own failure purely not being to withstand that level of boost and timing so early in the rev range as on gear change the cylinder pressures far exceeded anything that the oil pressure could prevent from making contact which is why it would only do it on short shift where it would drop straight down into peak boost/timing. Much the same as adding nitrous to a car too low in the rev range will make it throw a rod.

So the decision was made freshen it all up and save up for aftermarket management with logging capabilities and the back up of many years of I5 experience. With 125 channels of logging and safety cut outs based on oil pressure egt's etc I decided to go for the Maxxecu with the back up experience of Jonus.

This now means the car can be tweaked and adjusted based on logs by myself when needed without handing the responsibility to anyone else were not needed when any changes are made.
It also allows me to take my old carb, blow through carb and dizzy tuning skills and give them a fresh lease of life with a modern technology interface. this so far has let me finetune all driving upto 5000rpm and 1 bar of boost on the car to literally drive like a modern day car to put some serious miles on it (original engine had done 10k+ so would like to get this one loosened up as best as poss,) before jonus flies over from norway to map it in full.

I'm personally at this moment in time learning to map using the more modern interfaces compared to what i grew up with don't wish to take it on professionally as it is not my forte however it does help me further understand how changes in ve and flow dynamics of engine work I carry out effects the end result which is an amazing development tool for myself that I had not previously thought of.

[Jamo]

As usual jaw dropping stuff there JP, the maxxecu was something along with tatech I was considering going to go for as I realised the limitation of before oem and vems very intrested to see the results of it fully mapped up by Jonus!

[Sonic]

So the cylinder pressure was actually so high it was deforming the bearings??! Not sure i've understood that right, but if so that's mental.

I was quite impressed with the limited demo John showed me of the maxxecu... really cool stuff.

[JP]

@sonic in a nutshell pretty much yes. Normally such pressures lift headgaskets and bend rods. However these were strong nough in the design of the engine to withstand the pressures so it found the next weakest link which was the sputter bearings.

If there is a stronger bearing to try I would be up for risking another crank to see if we can overcome the issue but until then I'll be looking at making it come on power less aggessive.

[martinws]

That's an interesting issue. I wouldn't have ever thought that was possible without rods bending first.

What is the oil pressure around the bearing? Does the oil get pushed out and you get metal contact or does the oil stay put and act directly on the bearing to mash it?

[JariP]

Why didn't you just drop back the timing? Crushing the bearings just sounds like too early peaking cylinder pressures either from too much timing or preignition.

[prj]

Why didn't you just drop back the timing? Crushing the bearings just sounds like too early peaking cylinder pressures either from too much timing or preignition.

No preignition there, it's not E85.

Hindsight is a beautiful thing though. Of course now the timing or the boost can be dropped. But it takes some effort in finding out what the problem is.

How many exact engines like these exist in the world?

[mushasho!]

No preignition there, it's not E85.

Are you implying that pre-ignition only happens on E85?

[prj]

Are you implying that pre-ignition only happens on E85?

Not at all, but you have to get a lot of basics really wrong to get to that point on gasoline on one of these engines.

[JP]

@martinws. Yes normally you'd expect headgasket or bend rod first in that order. However as they along with everything else was belts and braces it found the next weakest link. Unfortunately the first 2 times it did it was impossible to diagnose as the symptons were of oil starvation with the typical melted bearing to crank and seized rod.

@jarip, ^^^^, also remember the issue didn't highlight itself during the 10hrs of mapping but we never did anything less than redline pulls backing of.or redline pulls and upshifting. It wasn't till during normal daily driving behaviour the issue highlighted itself. The first time it was down a steep hill and shifting at the bottom going back up the other side upto my house coming back from school run. So lots of oil surge round sump, oil had 10hrs of dyno and road mapping time on it and catchtank was half full. So naturally the first assumption one makes is oil starvation. It wasn't till the 2nd occurence happening on a level section of road on fresh oil and no oil in catchtank were the concerns came into play and the real investigation began. Like prj said hindsight is a wonderful thing can look back at it and go oh well that was obvious and yes he even send a file to sonic to write a pair of chips with some timing and boost pulled out of it to run until next time in town. However at this point I decided already I was going to pull everything and finish the bay the way I wanted to and get proper logging function in there which is ultimately essential for a development vehicle.

[Billman]

You still cant log in-cylinder pressure :-p

JOke aside, glad you did find the issue!

The question that arises in my head is how come and old/modern WRC car don't have these issues with 11:1-12:1 CR and 3.5 bar of boost?

[JP]

@Billman it's all rpm related.

Most race cars have power very late in rpm range less torque more hp. Because street car the turbo is little bit too small for optimum peak power in favour of early power. Earlier the power begins the more problems with strength.

Like adding nitrous if you add 100hp shot of nitrous at 4000rpm you get 100hp 80ft/lb for example take same 100hp shot of nitrous and add it at 1500rpm and you will ge your 100hp but 500-600ft/lb torque. This then starts to break stuff very quickly which is why all nitrous companies recommend to activate after min3000rpm.

The 800hp mk2 golf we did at one point had 650ft/lb of torque he launched the car once and the block twisted. This block was steel strapped girdled ductile linered everything done to it for strength normally cylinder walls would have exploded but the liners kept engine in one piece. but everything was cracked and pressuring water system.

So we put internals into fresh block sandpapered rings and filed piston grooves to make sure he could make next race meeting as waiting on parts was 3months being custom and changed map to 500ft/lb torque car had no problems for rest of season and ran pb of 10.1 on street tread. Same issue just more severe as was only small 1.8t engine with less block strength than i5.

[Billman]

that is why I mentioned WRC cars because the make big torque number down low the rev range.

[JP]

In which case we get to the stage of your guess is as good as mine. It's the first time this type of failure has happened to any of my engines in 17yrs of which in the last 3 there will be almost 150 of them of which 90% are above the 400mark.

This particular failure I can only draw conclusions from the mechanical evidence which was that it occured only at short shift were the rpm dropped to approx 4000rpm which was peak boost.