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Turbo Tel

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Delaware, USA

29th Oct, 2007 at 08:49:52pm


I had a perfectly set up engine but decided to do another needle with the leanoff pipe disconnected. I was nearly there and went off to a show in Maryland a couple of weeks ago and dispite the full throttle mixture being slightly lean (peaking at around 13.5) I thought It'll be OK if I take it easy, plus I got an intercooler now.. what can happen??

Well ...if you thrash the ass off it on the way home you can take the ring lands out on 3 pistons... (but boy was I having fun!!)

The first time I understand, but this time?? Could this be something with the GT15? It does seem to be putting plenty of power out but I was only running 8psi, 9:1 comp 266 cam, intercooler and 24degree max boost advance.

I'm really wondering now weather there really is a bad batch of Mega's out there.

Anyway if Avonbar ever get back to me I have a set of Accralite forged jobbies on order..Luckily the bores are OK.

Terry

website:- http://www.terryhunt.co.uk


BENROSS

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29th Oct, 2007 at 09:19:05pm

i think you may find it detonation which killed these tel

it seems to be occuring more now, maybe your right

any close up pics of these

Edited by BENROSS on 29th Oct, 2007.






Bat

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Bermingum

29th Oct, 2007 at 10:34:04pm

Hi,
Any idea what the charge temps are? This may be the key....
Cheers,
Gavin :)

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Turbo Tel

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Delaware, USA

29th Oct, 2007 at 11:43:58pm

Last time I looked it was mid/high 30's maybe hitting 40 in extreme cases, but not much above that. Should be a bit lower now that the temps are dropping.

Terry

website:- http://www.terryhunt.co.uk


minimole23

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Wiltshire

30th Oct, 2007 at 12:44:36am

Did minispares ever get back to you about the previous pistons?

On 7th Oct, 2010 5haneJ said:
yeah I gave it all a good prodding

BENROSS

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30th Oct, 2007 at 01:19:17am

Budd666 had the same problems

det killed these so iam lead to believe ?

Bat

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Bermingum

30th Oct, 2007 at 08:29:04am

Hi,
How about trying a home brew knock sensor? I don't see anything wrong looking about your setup.
Maybe 13.5 isn't enough fuel to help with cooling, as a spot too much fuel will help cool things down in there.
Cheers,
Gavin :)

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Tom Fenton
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30th Oct, 2007 at 10:08:26am

Looking at the RR graph for the DON, Dave Walker stayed below 12.5:1 AFR all the way from 3000rpm to 7000rpm, getting slightly richer as the revs increase.

OK, it was tuned for power, but maybe something to consider.


On 29th Nov, 2016 madmk1 said:

On 28th Nov, 2016 Rob Gavin said:
 I refuse to pay for anything else


Like fuel 😂😂

Turbo Tel

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Delaware, USA

30th Oct, 2007 at 11:08:01am

On 30th of Oct, 2007 at 10:08am Tom Fenton said:
Looking at the RR graph for the DON, Dave Walker stayed below 12.5:1 AFR all the way from 3000rpm to 7000rpm, getting slightly richer as the revs increase.

OK, it was tuned for power, but maybe something to consider.


Yes, thats just about what I aim for usually, still surprised that 13.5 would do this though..
I cleaned up one of the pistons with a scuff pad and there is absolutely no other signs of detonation on the top.
#1 has 2 broken lands, #2 the top has gone and #4 has some cracks.




Edited by Turbo Tel on 10th Mar, 2008.

website:- http://www.terryhunt.co.uk


Bat

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Bermingum

30th Oct, 2007 at 08:36:35pm

Hi,
Are your bores slightly under size?
ie ... What's the spec for bore size for the mega piston, is different to standard A series dimensions?
I'm thinking getting a little too hot and grabbing in the bore?
Cheers,
Gavin :)

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Turbo Tel

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Delaware, USA

1st Nov, 2007 at 03:11:16pm


The bore was set to the normal clearances but I'll measure it again. I dont see any real bad marks on the bore, some slight scratches on the piston but as the land broke maybe that was some shards.
Here's the plugs, this is after the 30 mile run that caused the problem, not really showing lean, rather the opposite in fact but maybe thats a factor? can overfuelling cause detonation to be more destructive? My O2 sensor wasn't showing rich but its always looked rich to me, maybe the sensor is wrong?


website:- http://www.terryhunt.co.uk


Bat

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Bermingum

1st Nov, 2007 at 08:05:22pm

Hi,
They look glazed, IIRC then means over heating. What number are the plugs?
Cheers,
Gavin :)

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Jay#2

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Northern Ireland (ex AUS)

1st Nov, 2007 at 08:23:09pm

Yeah I was thinking the same, they're shiny. Do you not get your block bored to suit each individual piston? What I mean is they are the second set of pistons in the block that was bored for the first set. All I know is my local machinist won't bore any block unless he has the pistons in his hand and has measured them up.

On 7th Nov, 2008 Nic said:
naeJ
m
!!!!!!sdrawkcab si gnihtyreve ?droabyekym ot deneppah sah tahw ayhwdd


fortfun

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Fort Collins Colorado USA

1st Nov, 2007 at 08:31:28pm

Tel, where is your wideband sensor relative to the turbo? Mine came with a warning to put it downstream of the turbo or the exhaust pressure variations could throw it off.

1275 with Back Door Turbo

Turbo Tel

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Delaware, USA

1st Nov, 2007 at 10:48:13pm



On 1st of Nov, 2007 at 08:23pm Jay#2 said:
Do you not get your block bored to suit each individual piston?


Well I did originally but wasn't getting a full rebore for the second set.

The sensor is about 8" downstream from the turbo outlet, in the downpipe.

Plugs are BPR7ES but they don't look glazed to the naked eye, I think its the flash being 4" from them thats giving that effect.

Edited by Turbo Tel on 1st Nov, 2007.

website:- http://www.terryhunt.co.uk


Nick
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2nd Nov, 2007 at 01:54:50am




On 30th of Oct, 2007 at 01:19am BENROSS said:
Budd666 had the same problems

det killed these so iam lead to believe ?



I've only killed one set of pistons, those were std metro turbo jobbies and it was definately down to det *blush* was a few years ago now though, about 6 weeks after i dropped my first turbo lump in and the actuator pipe fell off...was quick while it lasted though, lol.




I think i may have killed another piston now though, got a strange ticking noise which sounds like a really slack tappet but have checked and double checked them and they're all fine. I'm sure it made the same sort of noise when i killed the first set.

On 20th Oct, 2015 Tom Fenton said:
Well here is the news, you are not welcome here, FUCK OFF.

Turbo Tel

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1060 Posts
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Delaware, USA

2nd Nov, 2007 at 03:34:01am

Well as a "seasoned veteran" in detonated pistons I can only say that no noises were heard at all. The first I knew about it was sitting at a light and the idle was lumpy (due to no1 being down on compression) When I took off a cloud of smoke blew out the exhaust but that soon cleared. The big givaway is smoke from the breathers at idle which gets worse as you rev up. not much gets out the exhaust. No noises!! but if its been bad for a while who knows what else could have gone..

website:- http://www.terryhunt.co.uk

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