Internal engine geometry

Competition engines and ancillaries - general discussion
trickymex
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Internal engine geometry

Post by trickymex »

Hi

I just want to run an idea past the experienced eyes of users on this forum and of course Mr GC. I’m thinking of building a car to go racing with, there are as in any race series many different classes, the class I am thinking of entering has a few limitations. First of all I can change any part of the internals of the engine but I have to keep an un-modified block. Second, I have a choice with either two valves per cylinder or more than two valves per cylinder. For the two valve setup I can have a capacity up to 2500cc but in a multi valve setup (4v per cylinder) I would be limited to 2000cc

The class I’m thinking of entering is mainly made up of 205 GTI's and such like, some with Mi16 engine with power in the region of 250-270bhp, with car weights around 700-900KG. The car I am proposing to use in this class would be a Mercedes 190E Cosworth, the obvious problem is the fact that the standard engine come in either 2300cc or 2500cc. So here is my idea of solving this problem:

The standard 2300cc engine had a stroke of 80.25mm and a bore of 95.5mm and rod length of 149mm

This gives a bore to stroke ratio of 1.19
A rod to stroke ratio of 1.85

All nice but I need to bring the capacity down..


My idea is to run a short stroke of 69mm, with the standard bore of 95.5mm this would give me a capacity of 1977cc, a touch short of what I need but its unlikely that I will find a block that’s going to have nice fresh bores so I'm working on the assumption that i will have to rebore it, if I use 96mm as a maximum bore with the 69mm stroke I will arrive at a nice 1998cc perfect for what I need. To run this stroke I will be losing 11.25mm off the stroke, divide that by 2 = 5.62mm, this is what I will need to add to the rod length, so the rod length would now be 154.62mm, please someone confirm or correct this calculation I have made?
So to summarise the setup to run in the 2000cc class would be

Bore 96mm
Stroke 69mm
Rod length 154.62mm
A bore to stroke ratio of 1.39
And a rod to stroke ratio of 2.24


This is obviously a very short stroke setup and I have never seen such a rod to stroke ratio before, in theory it seem like a good setup for a very high revving race engine, the piston will spend a good amount of time dwelling at TDC for improved combustion, not to mention other benefits like less mechanical losses due to less rod articulation. My questions are, what are the potential negative points with this setup and am I going to an extreme with the short stroke setup that is just not going to work for what ever reason?

Basically I want some feed back on whether or not this is even going to work and the potential pit falls.

I am expecting a setup as I have suggested above would need a fair amount of maintenance and regular rebuilding but I am willing to do that. I would love to see what sort of power I can get from this engine, in 2500cc format in DTM I hear power figures of around 385BHP and in 2000cc setup I would be aiming for around 300bhp or a touch more, especially as the standard valves are 38mm inlets and 33mm exhausts, this is massive, I can’t think of any other road going engine that has valves this big and it seems to indicate massive potential

In this class I will be giving away a chunky weight advantage but I’m sure I can get it down to around 950-1000kg but with a power advantage and the RWD drive advantage im sure it will be fairly close racing, once, of course I learn to drive in a competitive manner! Anyway before I chuck huge sums of money at this I would like to hear all of your views but please bear in mind that I enjoy the engineering in most cases more than the driving but I still want to have a competitive car

Thanks in advance

Ricky
Rich Ellingham
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Re: Internal engine geometry

Post by Rich Ellingham »

Ricky, I can't comment on the engine idea, but I don't think you will make up the weight penalty over the smaller cars, remebering whatever you lose from the Mercedes get you nearer a road going 205, but you're racing 205 race cars with even less weight, and bhp doesnt mean a whole lot in the corners and on braking where the smaller lighter car will be faster - usually.

Could you look to a honda civic or something with a good power to weight starting ratio??

Rich
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trickymex
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Re: Internal engine geometry

Post by trickymex »

Actually Rich

I think you run in the same series, please correct me if im wrong, its the DMN series and im aiming for class C

I know a fair few people running in DMN, graham bahr,andy pipe,and soon to be dave white, and they are all very nice people

Anyway back to the car

I know the weight issue is going to be problem but graham is running an e30 in the same class and they are not that much lighter than the merc, admitadly he has not run it yet so i cannot comment on how competative it is

Also i have a contact in Germany that can help with alot of the old DTM parts, i know it will be expensive going this way but i think it will be worth it, and i can get carbon parts made sort of cheaply so i can change things like the boot,bonnet,doors for lighter items
Rich Ellingham
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Re: Internal engine geometry

Post by Rich Ellingham »

Yes I was out classed, I suffer without doubt from maybe a not great set up, but I have no doubt that any development on my car would be solely aimed at weight. If you consider LMA class D champion this year Andy Neal, who ran a Honda Integra type R 1.8 DC3 modified estimate 230 bhp. He ran away with the class win, but the car weighed only 880kgs race ready, a clear 120 kgs+ lighter then mine, despite the small 20hp power difference the benefit in acceleration and handling were clear especially compared to fellow competitors in the same class.

Money spent making a heavy car light is better spent optimising a light car into a class winner. Please visit the TSL timing web site if you wish to see your competitors times (look under different clubs as the BARC SE share with MSV and maybe others), pay particular attention to the smaller cars. I know where I'd put my money if I had to start again.

Regards

Rich
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trickymex
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Re: Internal engine geometry

Post by trickymex »

I take your point Rich,

What weight do you reckon I will have to get down to with the Merc to be competative in that class?

The other option is to stick with the merc, keep the 2300cc or 2500cc, and move up to class B, this also gives me the option to turbocharge it, in this class though I would have no other choice to be competitive as this class is full of 450+bhp monsters like Trevor Nicosia's 2.4 turbo Kappa

And can you think of any other rear wheel drive cars that could be competitive in class C?
Rich Ellingham
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Re: Internal engine geometry

Post by Rich Ellingham »

Mk 1 and 2 escort.

I think you would need to be in the 800's for the merc to take out the competition, which I don't think it will get to without huge weight saving. A really well developed (i.e. Professional builts car) may well make up for a weight penalty. I do know the high powered RWD cars do suffer in the wet, I usally pass the cosworths in the wet, and both LMA m3's saw the barriers in the wet this season. Plus with the fwd you dont have propshaft weight to deal with. DMN dont allow traction control either.

Also I'd never endorse building a car over a ready built car, especially of challenge of trophy spec like Clio cup, vectra challenge, Tomcat challenge cars. They may seem fairly simple but they were all developed on budgets well outside of a privateer club racers and then duplicated to sell for a series. Most have gearboxes that would cost more then the entire purchase of the race car to replace or spec; I think they represent very good value and a good starting point, and numerous series now would allow them to be modified above their std race trim.

rich
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trickymex
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Re: Internal engine geometry

Post by trickymex »

I have thought of an escort, I have had 7 mk1 Escorts in various conditions but have you seen how much they cost now for a decent shell?

Needless to say they are extremely expensive to buy and modify to be competative and on top of that the panels are rare and expensive to replace, and no doubt I will be going through many to start with

As you say I may just have to look at something FWD but I will investigate some other RWD cars first

Ricky
Last edited by trickymex on March 5th, 2009, 11:08 am, edited 1 time in total.
Testament
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Re: Internal engine geometry

Post by Testament »

It doesn't sound like the merc can be competitive without alot of work and development. Are you entering the racing series because you are an enthusiast for a particular make/model of car, or because you want to be competitive and go for race wins?

if its more of a fun/enthusiast thing then I would be using the car that I like and enjoy driving hard, never mind the ultimate placing. If you want to win it comes down to choosing whats the best base car with good aftermarket support and parts availability. If you are determined to use RWD it does limit your choices/force you to look at older models, or reduce your available support since FWD is so much more common now days.
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Re: Internal engine geometry

Post by Guy Croft »

Respected members!

Interesting thread which many will read as usual.

In order that might carry more weight than most similar posts on other forums please in your enthusiasm do not forget to respect proper capitalistion such as

I not i
Merc not merc
and Cosworth not cosworth.

Some of these are famous names and deserve a capital letter if nothing else.


Thank you.

GC
trickymex
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Re: Internal engine geometry

Post by trickymex »

It's not that I'm an enthusiast for any paricular car but I am a fan of RWD, the Mercedes 190E cosworth seems to tick all the right box's apart from the weight disadvantage

The standard engine screams out massive potential, I can't think of any other engine that has such huge valves, it also has a good gearbox, the same as the E30 M3 and a LSD as standard, on top of this they are cheap to buy and panels and spares are relativly cheap

Being this car was used in DTM also means a wealth of information on how to make them competative is at hand


But fundementaly if I can't make the car competative then it's pretty much a waste of time, money and effort, unless I can enter this car in a different series where it will be competative?

The other option I thought of was a Sierra sapphire Cosworth, cheap enough to buy and make quick, lighter than the Merc and slightly wider with a slightly longer wheelbase but for this class I would have to convert the standard engine to N/A and that's alot of work and cost but it could be a viable option
Rich Ellingham
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Re: Internal engine geometry

Post by Rich Ellingham »

Hi Ricky, you mention the idea of the DTM 190E being some kind of prompt for making a road going 190E a race car. I think you will find that any car to do with DTM is not too far removed from just a silhouette with incredible amounts of development and custom fabrication. Thus virtually no applicability to a road car, I base this assumption on the difference to the Alfa Romeo 155 D2 touring car versuse the 155 Ti V6 DTM car, where by the D2 can be seen to have the basic shell with standard pick up points for the very custom subframes the DTM car infact had a partial space frame on the front end. I know the company Xsport ran a evolution 190E for a few years recently. I don't think as a club racer you could afford to pay for such custom parts in a bid to make such a car competitive within the proposed class. It's well known that Escort Mk1 and Mk2 shells are valuable items although it's fair to say they still have spares available for them readily and virtually any custom race part you care to mention without resorting to custom one-off's as the Mercedes might dictate.

I would consider the idea of a pre-builts Escort Mk2 as they don't seem to be up there with Mk1 prices. Incidentally there are few in the DMN one of them is a 2.0 Pinto 8v which still turns very impressive times, so I don't think you'd have to go all out from the start regarding engine. Would you consider a more focused challenge like the MR2 racng series, they now have 4 class I believe for al the naturally aspirate MK1-3 and turbo Mk2, RWD also?
book 38
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Re: Internal engine geometry

Post by TR-Spider »

Hi Ricky

First: I think your calculation with the stroke/rod is ok.
As information: BMW did downsize the 2.3l M3 E30 to 2.0l for the italian 320iS by reducing the stroke from 84mm to 72.6mm (bore 93.4mm).
But for the Merc that means a custom crankshaft and rods, which will be expensive, no?

Second: The 190E in road spec was around 1400kg, compared to M3 1200kg, where certainly not all of that difference is luxury carpet weight on the Merc...(think 2 extra doors). I know that an M3 is very hard to get below 1000kg, so most likely the Merc will be heavier.
That really gives you a big disadvantage to start with.

So, why not take a closer look into the BMW E30 direction? Choice of 318is (1.8l), 320iS (2.0l from italy), M3 (2.3l) There are certainly a lot of parts available. And they are nice cars to drive...

Thomas
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trickymex
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Re: Internal engine geometry

Post by trickymex »

Rich, I understand that the DTM car has very little to do with the road car but i was refering more towards the developments that was done on the DTM car and copying some of the ideas to help with the car and hopefully making it more competative

But if the car cannot be brought down to a reasonable weight then i think i may be looking elsewhere, as you said the weight is more important than the ultimate power in this class and unless i can make it competative then im kind of waisting my time

Thomas, Thanks for confirming my calculation, as for the cost of custom crank and rods, well i would be going for after market rods a pistons as a minimum no matter what car or engine combo i go for, the crank will be expensive no doubt but the way i look at it is if i build this engine for racing then i would need a nice fresh crank to start with even if i stick with a standard item its unlikley that i will find and un-worn good condition one in any of the second hand engines that i will start with, so i will end up buying a new standard crank and the cost will be cheaper than an after market item, yes but for the extra cost i would just pick out a nice after market one for peice of mind, that may seem a touch overboard as i could get the standard item ground, balanced and checked and it would be fine but i would rather have peice of mind rather than save a few quid

As for the E30, its a very good suggestion, the reason i avoided the E30 was that i love the S14 M3 engine and if i was to go the E30 route i would want to use that engine and they cost a fortune and they are rare and as far as i know they never put a 4 pot 16v engine in the E30 apart from the M3 and 320is

If they did a 320 4 pot 16v then i could go that route but as far as im aware they never did and that means the choices i have are a 325 6 pot (2 valves per cylinder) or M3 S14 with a lowered stroke to make it fit in the 2000cc class

But i think your right the E30 could be a more competative option, there is an E30 in this class, that is running a 2500cc 4 pot 8v but i would prefer to go the 16 valve route

Thanks everyone for your help

Ricky
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Re: Internal engine geometry

Post by Testament »

Mk2 Escort with a sierra cosworth YB engine (16v 2L, running naturally aspirated instead) can make a very fast package which would be of similar weight and power to those Peugeots. This is all presuming very good preparation and a healthy budget, which will be neccesary to get any vehicle to be competitive.
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trickymex
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Re: Internal engine geometry

Post by trickymex »

unfortunatly the rules stipulate that I can only use an engine that was originally fitted to the chassis, the only engines they ever fitted to the mk2 or mk1 escort was the 8 valve crossfiow, the 8 valve pinto or in the rare rs1600 and rs1800 was the 16v BDA, great engine with plenty of potetential but very delicate and extremely expensive, sorry I forgot the early mk1 lotus twin cams, good engine but again very expensive


The reason I want to avoid a classic ford is mainly because they are almost all rotton, unless I buy one rebuilt already and the money they cost is on par with an ex 1990's btcc rolling shell

here is a pic of my last escort

Image
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