My Twin Turbo

Dave · September 16, 2012, 00:23:17

Yes I know mate the comparison picture is a STD TT T2 compared to my GT2252's.

Your GT2056's have even more axial flow than mine.

The Garrett turbine maps are based on no wastegate control & it's said the wastegate can usally flow another 10 - 15% of extra exhaust when open.

So if you increase the size your actual increasing the max flow of the turbine.

Can't see any harm if you want to enlarge it a few mm, how much is your call as you have them infront of you.

It would still be better if you kept the two flows away from each other at the back of the turbo as much as possible.

T4T · September 16, 2012, 00:36:56

Those bearings are ok

I used to run silkolene 10W60 in the 280 .
I have heavy duty bearings for the new engine .
I was told to use them because of the increased forces .

Running without the squirters , I thought they were to help with the oiling issues common to v6's on the thrust side of the bore .
Is this sort of tune for the engine now just sorting one problem but creating another ?
I'm guessing you haven't had any issues with the cylinder wall / piston skirt .

This is one of my old pistons and rods .

[attachment=1][attachment=2]
Had this happen on cylinders 2 and 5 ( pictured )

No one has ever been quite sure why .

Re : exhaust
I 'll have to see if there can be a dividing wall put in that extends into that cutout .
Why did they do that ?

I've even read a paper from a garrett advisor stating that it's better to separate the flows for the first 12-18" .
Don't have that much space though !

Matt

Dave · September 16, 2012, 01:02:09

Hells bells that's pretty bad!

Was a blocked hole the cause of that then?

Thing is we are talking a 1960's design, oils where very different back then.

Modern oils do there job much better now, if you fitted fancy rods you would not have that squirter unless you speced it or drilled it yourself & they don't think it's an issue.

I took a chance to try & cure a big problem for me, so far I have cured the problem & have no issues with the pistons.

I read once that the engine started life as an industrial engine so would be static, if that is true it explains why they had the oil squirts in the first place.

T4T · September 16, 2012, 01:42:09

No oil supply problems at all , no pressure issues and no blockages .
When the engine was stripped found this .
Cylinder walls were almost perfect which you wouldn't believe looking at the pistons .
Obviously aluminium is softer but even so .
And no tell tale noises to suggest contact was happening .
It was really weird .
Engine ran great with no smoke , gobsmacked is probably the most apt term when splitting that engine .

BTW have you changed the bearing type while solving your big end probs .
Just wondering if that has had an impact .

Matt

Dave · September 16, 2012, 02:03:21

Used Fords, ACL & Clevite all failed.

The last ones fitted are Fords.

Looks like something has passed by the piston but stopped at the oil ring.

What was you doing when it happened or did you never know as it was like it when you pulled it apart?

capri v8 driver · September 16, 2012, 06:52:02

Did you checkt the clearence of the pistons? looks like they are to tight.

T4T · September 16, 2012, 09:55:54

Never even knew it was happening , so a little unsure as to how long it had been going on .

Paul , this was a tt280 built by TT in Northampton using their AE forged pistons which only came in the one size - Std.
These pistons had done 105,000 miles .

Now you've seen the photos Dave
When you said last night that you blocked the squirters , the picture of these two pistons came back to haunt me , not that that was the cause though .

Did you make all the changes at the same time - oil grade , pressure , squirters ?
It seems to me that the squirters will only actually squirt once every engine revolution and the rest of the time they are just an oil leakage point .
Or am I missing the point .
That leakage considering the size of hole in comparison to the circumference of the rod journal x2 is negligable isn't it ?
Just thinking that with 10W60 oil and increased base pressure , would those 2 have cured the problem by themselves ?

Matt

Dave · September 16, 2012, 23:03:05

QuoteDid you make all the changes at the same time - oil grade , pressure , squirters ?
It seems to me that the squirters will only actually squirt once every engine revolution and the rest of the time they are just an oil leakage point .
Or am I missing the point .
That leakage considering the size of hole in comparison to the circumference of the rod journal x2 is negligable isn't it ?
Just thinking that with 10W60 oil and increased base pressure , would those 2 have cured the problem by themselves ?

I used STD 10w 40 oil & that allowed damage to every big end, changed to Millers 20w 50 & increased pressure to 65psi, that was better only one showed damage but later another spun so that's when I changed to 10w 60, bigger pump, 70psi & blocked squirts.

Yes they only squirt once per revolution.

The big ends need all the oil they can get as basically the surface area is too small for the loads.

I think I am just getting away with it, will see what happens at 2 bar LOL!

The uprated FBE's & pretty much all the top Ford v6 race engines from the like of Ric Wood run wider big ends!

However it's a lot of money!

T4T · September 17, 2012, 01:12:54

You have to question one's sanity when big end bearing's become service consumables .

I will speak to my engine builder about this . Rather worrying if it's going to stop the engine reaching it's potential .

Did Gengis have any similar issues or did he go down the same route as you have .

Matt

Have cast my eye back to your stealth engine build thread . Were those shot bearings back on the t2 turbos .

Dave · September 17, 2012, 09:15:56

It's when you talk of tracking it mate, sets off alarm bells.

Seriously tracking a car/engine is a different thing to a road based car that does the odd dyno, 1/4 mile & maybe 2 hours of track time in a year.

You run it at full power for the dyno shoot off & basically 3/4 power for everthing else.

Otherwise it will die unless it is built from the start for the track.

You need to be dry sump for a start, on 0-100-0 testing a STD Minker's oil light will come on for a good second or two.

I could go on & on to be honest.

You only need to be aware of the limits, do what you can to address the problems & enjoy driving it.

Geoff's track car is reliable for what he uses it for but the sister engine was used on track racing & proved to be completely unreliable!

It's why an experienced builder will ask the most important question, What do you intend to do with the engine LOL!

T4T · September 17, 2012, 15:11:33

Dave , have you tried chamfering or tear dropping the oil ways on the crank ?
Possibly cross drilling the big end journals as well .

I'll mention these to my engine guy when I drop the lot off next week .

Matt

T4T · September 17, 2012, 17:07:52

Thought about modding the front slam panel ....... nope !

Special radiator that was twice the size of standard had a hair cut to remove the top 3" .

[attachment=1]

I can now have the intercooler outlet splitting into two 2 1/2" pipes coming into the engine bay under the slam panel .

[attachment=2]

[attachment=3]

Because the rad is triple core it's still about 50% bigger than std capacity and about 95% of the frontal area .
Should work nicely I hope .

Dave · September 17, 2012, 21:47:58

Looking good!

QuoteDave , have you tried chamfering or tear dropping the oil ways on the crank ?
Possibly cross drilling the big end journals as well .
I'll mention these to my engine guy when I drop the lot off next week .

No didn't try any of them, crank is a 24V one untouched.

It's something your engine builder has to decide as he would get the blame if the worse happened.

Increase oil pressure, thicker oil & less leakage are the big three.

But also what you mention would probably also help.

The builder just needs to be aware of the problem so they can advise the best soluction that they think will work.

BUT remember your not curing the problem, your pushing the limits of a bad area that's all.

This is what I think happened to your pistons. Yet more stuff to scare you!

[attachment=1]

T4T · September 17, 2012, 22:17:00

Yep .
That could have been one of my two .
Interesting about potential coolant problems .
Mine used to get hot very quickly on boost . Always backed off before seeing dangerous temps ,
but localized hot spots may have been there . As I say , nobody could point their finger at a definate
issue when the engine was stripped down .

T4T · September 19, 2012, 20:19:18

Just a couple of pics to interest peeps .

[attachment=1]
Had the turbotechnics manifolds sleeved to locate them better on the studs .
[attachment=2]
Free floating rockers . There to do a job , but I think they look fantastic .

The Inlet side of world products heads is very different ( better ) than std heads .
Exhaust side much more similar but still different .
The rusty looking one is from the good old usa .
[attachment=3]

[attachment=4]

The world head ports as you can see are very straight compared to std and are larger too .

I don't have any photos of the engine work done at the mo .
I'll try to sort some when I have the chance .

Matt

Dave · September 19, 2012, 22:03:49

Nice.

The world heads are a lot like the last 94-96 Ford heads.

They look almost identical but the world heads are over 1kg heavier so defo have more meat!

revhead · September 19, 2012, 22:46:53

Quote from: Dave on September 16, 2012, 01:02:09
Hells bells that's pretty bad!

Was a blocked hole the cause of that then?

Thing is we are talking a 1960's design, oils where very different back then.

Modern oils do there job much better now, if you fitted fancy rods you would not have that squirter unless you speced it or drilled it yourself & they don't think it's an issue.

I took a chance to try & cure a big problem for me, so far I have cured the problem & have no issues with the pistons.

I read once that the engine started life as an industrial engine so would be static, if that is true it explains why they had the oil squirts in the first place.

A friend and I recently took apart a Honda CX500 V twin from 1979 and the rods had the same oil squirters as a cologne, which I couldn't understand as a bike engine would lean constantly from side to side?

JFB Tech · September 19, 2012, 23:44:33

Quote from: revhead on September 19, 2012, 22:46:53

A friend and I recently took apart a Honda CX500 V twin from 1979 and the rods had the same oil squirters as a cologne, which I couldn't understand as a bike engine would lean constantly from side to side?
[/quote]

The CX engine was originally designed as a fore and aft Vee so would have been more likely to suffer from starvation during acceleration and braking. Not sure what bike it was for originally as I think all the Maggots had it mounted across the frame.

T4T · September 23, 2012, 18:55:03

Hi
Trial assembling the engine at the mo to ascertain if I have dealt with everything I can
before the engine goes to the builders .
Where does the oil distribution block for the turbos attach ?
Is it to the lower front engine mount bolt and just use a longer bolt ?

Cheers
Matt

Dave · September 24, 2012, 21:06:49

Yes that's where TT put it.

If you don't have aircon then you can mount it directly above the block oil outlet near the head where it suits it better.

T4T · September 26, 2012, 00:46:40

Rear engined bmw

Centre of gravity is a little high for my liking .

Should be the beginning of November when engine and box go in the car . I hope .
Fingers crossed !!

T4T · September 29, 2012, 20:27:00

Been too busy to post recently !

Having talked to my engine builder when I dropped it off I thought I should share his thoughts .

My pistons look the way they do because they have got too hot !

This was caused by the oil breaking down - again due to temperature - the cause of which may have been the previous owner using
the wrong oil , or a localized cooling issue in the block . The block is being inspected closely to make sure it doesn't happen again .

The problems with big end bearings as experienced by Dave and perhaps others is ................

HEAT !

Basically the massively increased pressures being applied to the big ends is momentarily cooking the oil causing it to start
breaking down . If I have understood him correctly , then any inconsistencies in the oil , or bearing surface , allow excessive pointload pressure
(not the full width of the bearing) which attacks the thin bearing surface forcing it to start to break up .
Of course once this starts , it self accelerates .
He has seen this problem many times , on all manner of engines that have been brought to him to build/tune including racing engines.
All of them have failed because of two reasons
Tuning engines way beyond what they were initially designed for and not dealing with the resulting forces adequately
Or
Revving engines much higher than they were initially designed for and not dealing with the resulting forces adequately .

I would say at this point that he is a very well respected engine guy , across various forms of motorsport but I'm not going to advertise his name in case
my portrayal of what he told me is not good enough .

Anyway , the solution is more oil flow , and the right grade of oil . Simples .

Oil flow is being dealt with by a melling pump I already have and the correct grade of oil for this engine being ...........

20w60 semi synthetic for endurance racing . NOT fully synthetic !!

He is chamfering the oilways in the crank journals slightly , and that is it .

Please feel free to discuss this in case I haven't passed on the info very well !

I will be doing exactly what he has advised , and he's not expecting any problems with big ends .
We are however using good quality heavy duty bearings as normal bearings are too soft and have the potential to deform .
I hope this is useful to people .

Cheers

Matt

capri v8 driver · September 29, 2012, 21:22:27

QuoteAnyway , the solution is more oil flow , and the right grade of oil . Simples .

And a decent oil cooler.

Heat problems is nothing new with the colone engine, even in stock form, when pushed hard, they overheat, starting with the oil.

T4T · September 29, 2012, 23:01:51

Paul , the oil is only cooking while it is under enormous stress in the big ends .
The average oil temp will not show as a problem .

Yes the oil needs cooling generally when the engine is pushed hard and that is solved by a cooler .
This situation in the big ends will not be helped by keeping average oil temps down .

Matt

capri v8 driver · September 30, 2012, 07:42:15

QuoteThis situation in the big ends will not be helped by keeping average oil temps down .

No your right, but its a start.

More oil volume and a biggere bearing clearance does help. But to really tackle the problem, you need to redesign the crank and rods bearing surfaces and journal size.

T4T · September 30, 2012, 08:32:38

"More oil volume and a bigger bearing clearance does help. But to really tackle the problem, you need to redesign the crank and rods bearing surfaces and journal size."

Yes , as Dave has pointed out earlier in the thread , increased journal width is the ultimate solution . But I really don't want to have a crank and rods made specially .
I don't actually know if that would be necessary , but I wouldn't imagine the std crank taking too kindly to being butchered to increase journal width significantly !

Oil cooling of course always helps and having increased the flow assists the job of a cooler in this regard .

Matt

Lemon-Ade · September 30, 2012, 10:17:01

Very interesting stuff Matt

and thanks for sharing your developments

capri v8 driver · September 30, 2012, 11:02:18

QuoteYes , as Dave has pointed out earlier in the thread , increased journal width is the ultimate solution . But I really don't want to have a crank and rods made specially .
I don't actually know if that would be necessary , but I wouldn't imagine the std crank taking too kindly to being butchered to increase journal width significantly !

From a economical point of view it will be to expensive to do these mod's and a other problem will be the block it self, that doesn't have enough material in the mains, making the journals bigger, the block will lose strenght. its the same for the stock rods.

Its strange nobody mentions a oil accumulator as most bearing problems are caused by a sudden drop of oil pressure.

T4T · September 30, 2012, 15:32:20

One of those would certainly help with oil surge if running the car really hard .

I've never heard of them before .
Thanks
Matt .

JFB Tech · September 30, 2012, 21:40:27

Have a look for Accu-Sump, they do oil accumulators, they can be rigged for pre-oiling before start up or to supplement oil flow when the pressure drops.