M103 detuned...?
I'm fairly certain that someone posted a remark about the M103 in a G being a "detuned" version of the M103 in a car. Can't remember who posted it or what exactly what was written. Did a search and can't find it either. Any ideas anyone? I'm keen to know more about this.
Thanks
Whirr whirr ching ching - could it be this - http://www.gwoa.co.uk/content/g300-thermostat
Arnie's comment No. 7 about half way down.
Hi Ian
There are two quite a lengthy and detailed threads about turbo charging a M103 engine in these links...
http://www.peachparts.com/shopforum/performance-paddock/251302-190e-3-0-...
http://www.peachparts.com/shopforum/performance-paddock/174080-300e-12v-...
Although they relate to saloons rather than the G you might find them useful. They have apparently been getting over 600hp out of the M103 on standard internals 
.
Thanks for that. The first link gives "page not found"
I'll have a closer look at the second later.
The first link is fixed now.
The first link is fixed now.
Thanks, interesting reading.
I wonder if anyone knows the CR for the M103 fitted to a G. It's 9.2: 1 generally, but I was wondering if it was lower in the G.
Main reason I'm interested is that I'd prefer not to go down the Megasquirt route if possible. I did try Turbo Technics to see if they could advise on the recommended CR, (given that they were the guys that shaved the pistons!) they were however a complete disappointment. A waste of time, petrol and telephone costs; hopeless.
It seems to me that the best, (least electronic) alternative would be a custom thicker gasket. But to get that fabricated I need specs. What joy!
PS. If anyone can come up with the specs, I'd also need someone competent/reliable to fabricate the gasket!!
EDIT: Come to think about it, I think TT shortened the con rods ..... doh!
http://www.mbclub.co.uk/forums/engine/110088-m103-compression-ratio.html
and
http://www.pointedthree.com/disc/forums/showthread.php?tid=14354
Thanks for that. Those posts confirm that the M103 CR is 9.2 : 1 What I don't know is if the G M103 has the same CR.
Some preliminary info I have from folks who have the TT TT fitted in a 109E is that: "as long as it's around 9:1 you should be ok" I'm waiting to see if MBUK can give a definitive response.
Somewhere in the back of my mind the figure 8.8:1 as optimum keeps cropping up. No idea why.
Does anyone know how to accurately calculate the thickness of a gasket to reduce compression?
i think that there is very little difference between 9.1 and 9.2. Gasoline engines use a throttle so the cylinder is hardly ever 'full' of air to begin with. The amount of air compressed depends on the throttle position. A CR of 10:1 is more normal for a high-performance, naturally aspirated engine., so going to 9.1: 1 or 9.2: 1 would make little difference, I think. If pre-ignition is a concern, just use higher grade fuel. The premium fuels will give higher mileage anyway. Or you can change the resistance plug to set the engine ignition timing for a lower octane.
As for making a gasket. you can work out the compressed cylinder volume (1/6 x 2960 / 9.2) in CC and then work out the effective cylinder compressed length from that = (Pi x r^2 x L), where r is the cylinder radius ( = [88.5 mm / 2], I think - need to check)
so, L1 = (1/6 x 2960 x 1000 / 9.2) / ( Pi x r2 ) (note x 1000 to convert CC into mm3)
Then, do the same for a CR of 9.1:
L2 = (1/6 x 2960 x 1000 / 9.1) / ( Pi x r2 )
required gasket thickness = ( L2 - L1 ) in mm
Thanks for that, very helpful. The minimum reduction be suggested is 9.2 : 1 to no more than 9.00 : 1 which is what makes me think the 8.8 : 1 rattling around in my head is possibly correct.
You reffered earlier to the M103 in G's as being "de-tuned", was that a reference to reduced CR?
Thanks.
Hi Ian
I know you said that you did not want to go down the aftermarket ecu / fuel injection route but that is the easiest way to control any issues with pre-ignition when running a turbo.
With a modern programmable ecu that can alter ignition timing to suit different levels of boost there is no longer the same need to reduce the compression ratio. I imagine that it might work out cheaper than the machine shop as well.
Thanks for all the input folks.
From my reading it's clear that an alloy gasket on top of the existing gasket is not a good idea.
That leaves the options as:
a) Con-rods [I now have a formula for their reduction]
b) Pistons [probably too expensive and creates extra work]
c) Electronic.
From the reading I've done, it seems that the Megasquirt [or equivalent] route is the way to go. I'll go over all the options with the guy who's doing the work and I expect that we'll decide on electronic.
I've gone into this in some detail as (rightly or wrongly) I would have preferred a non electronic solution. Probably because I don't really understand those boxes of tricks, whereas I do have a basic understanding of the other methods.
Nine weeks to installation, I'll ask my guy to takes some pics as he does the installation and keep folks posted.
Once again, thanks for all the input.
Sorry I'm asking, but do you think there is room for a t/c? I had a look into my car and it looks pretty full up with the a/c compressor, piping ABS module, alternator snorkel etc etc heat shields . I am told that for this engine, "porting" and changing the inlet valves is probably a better way to boost up. No major surgery, running gear remains the same , no special lubrication or cooling. Unfortunately there is no way of re-mapping the ECU, otherwise this would have been probably the less painful way of acquiring the extra horses.
Sorry I'm asking, but do you think there is room for a t/c? I had a look into my car and it looks pretty full up with the a/c compressor, piping ABS module, alternator snorkel etc etc heat shields . I am told that for this engine, "porting" and changing the inlet valves is probably a better way to boost up. No major surgery, running gear remains the same , no special lubrication or cooling. Unfortunately there is no way of re-mapping the ECU, otherwise this would have been probably the less painful way of acquiring the extra horses.
I can't say that this is an issue anyone has raised. I do know that they were fitted to W124's and I also know that it's been fitted to a W201. On that basis I'm thinking there will be sufficient room.
I assume that a 3.2 24v transplant is not the answer to the question of more power?
I'm not sure that would increase the power so much compared to the TT. In any case I think that route would be it would be v expensive. I have the TT kit already and I expect the installation and bits to come to around £2K. No idea what a transplant would cost but I suspect it would be more.
EDIT:
Just checked the figs:
M103 188bhp
M104 220bhp
See range for TT attached
No contest then!
I did have a M103 engined Mercedes for 5 years and the only problem I encountered with it was distributor caps. It needed a new one every 12k miles.
Good luck with the installation - it is nice to see upgrades on a petrol G.
The 3.2 m104 engine would not be compatible with the ke-jet system in the ge300, it would need the head off a m104 24v 3 litre engine which is k-jet, altogether too much fuss.
Forced induction is better at giving the torque needed in a hefty vehicle.
The higher octane fuel now available might mitigate the need to fit shortened con rods as specified in the original conversion. I belief the highest octane fuel now available is higher than that available in the late 80's when TT conceived the system
The 3.2 m104 engine would not be compatible with the ke-jet system in the ge300, it would need the head off a m104 24v 3 litre engine which is k-jet, altogether too much fuss.
Forced induction is better at giving the torque needed in a hefty vehicle.
The higher octane fuel now available might mitigate the need to fit shortened con rods as specified in the original conversion. I belief the highest octane fuel now available is higher than that available in the late 80's when TT conceived the system
I've probably got this wrong, but I thought lower octane fuel was better when running turbo chargers...??
the instructions for fitting insist on what was then 98 octane fuel
http://www.supercars.net/cars/4531.html
http://forums.mercedesclub.org.uk/archive/index.php/t-38989.html
the instructions for fitting insist on what was then 98 octane fuel
http://www.supercars.net/cars/4531.html
http://forums.mercedesclub.org.uk/archive/index.php/t-38989.html
Thanks that's clear, and I'm guessing TT know more about it than some bloke on the net......
I'm pretty sure its in the paperwork, but the advantage is less work modifying the pistons or shortening the con rods
I've probably got this wrong, but I thought lower octane fuel was better when running turbo chargers...??
From what I understand Octane Rating is a measure of how much a fuel can be compressed before it detonates without an ignition source.
High performance engines, normally aspirated or turbo charged, need a higher octane fuel because of the higher compression and increased heat they generate which would cause detonation (knocking) with a lower rated fuel.
You can get around the detonation problem with standard fuel by retarding the ignition (which is what a modern ecu does) but then the engine is not running at its optimum level of performance.
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Whirr whirr ching ching - could it be this - http://www.gwoa.co.uk/content/g300-thermostat
Arnie's comment No. 7 about half way down.