Martin-Hadland

iTrader: (2)

The calculation is not difficult!! It's rod length divided by stroke, std rod is 128.5mm & std stroke is 77mm (76.95 actually)

J1mbo

iTrader: (1)

i wasnt saying your calculations were wrong i couldnt be arsed to get a calculator so seeing as your were there .. perfect lol so now i await marks awnser as to why you would go for a not so good rod ration if it is possible to get a better one

Martin-Hadland

iTrader: (2)

It's all about juggling about what you can get inside the std block, or not in my case

J1mbo

iTrader: (1)

engine im thinking of has a rod angle of about 1.78 i think and thats standard block height not bad really
iirc yours could be better am i right ?

RWD_cossie_wil

iTrader: (9)

What does Rod ratio tell you? I take it the higher the number the better?

Mike1

Power Engineering ( as mentioned before ) used to do the 2400 kit. I have an article from the old "Top Car" mag about Mark Lovell driving a 2wd and 4x4 version back across France in them. Promised to scan it in ages ago for user Evo200 but I forgot ......

Will try and do it in next couple of days

Mark Shead

To have a better rod ratio would mean having a shorter stroke, But I am happy with the ratio I have and have no problems with it as I dont want or need to rev the nuts out of it, My pistons speeds are well within what I want and deam safe.

Mark

J1mbo

iTrader: (1)

ahh right okii

RickyLee53

Yes,

It tells you a number of things, piston speeds (acceleration), side loading on pistons, stress on components etc.

evo200

iTrader: (1)

Forgot about that too mike!!!!! Must have been a long drive to Rome eh!

Martin-Hadland

iTrader: (2)

That conversion IMHO is not the way I would go, I'm sure they used a 92.8mm bore and 88mm stroke which makes 2380cc. Very torquey low down but harsh at higher revs, 1.36 rod ratio.

Mike Rainbird

iTrader: (3)

Is there an echo in here?

Martin-Hadland

iTrader: (2)

Nope, your reply was vague with no info to back it up! At least there's plenty of figures on this thread for you to jot down!!

Mike Rainbird

iTrader: (3)

It was designed for the layman and imparted the same information without confusion .

However, point taken:

Standard rod angle / mine = 1.66
2.4 rod angle = 1.36
Your rod angle = 1.80
Harvey's rod angle = 1.78 (but no extra capacity)
Rod's rod angle = 1.60

It's Czech Mate

It took an hour for that reply.......was Harvey busy taking a dump?

Mike Rainbird

iTrader: (3)

All the information is available in this thread (although you may have been too stupid to notice ), I have just amalgamated it in one post, so you can see the differences .

J1mbo

iTrader: (1)

lead_foot

iTrader: (1)

Might be intresting reading:

http://www.stahlheaders.com/Lit_Rod%20Length.htm

http://www.chevytech.net/2c27o1.html

blgdave

What would a Holbay YB Stroker crank be worth these days?? I have a full YB 2.4 Holbay stroker engine in my shed but cant find one of the rods. I was thinking of either building it back up or just selling off the crank and keeping the rest as spares.

Worth doing or no??

Chip

iTrader: (3)

Massive sweeping generalisation there, and not a very accurate one.

Longer and shorter rod ratio each have benefits depending on the rpm you are running and the compression of the engine, and the boost you are running.


A smaller rod ratio can be particuarly good for midrange torque for example.


A rod ratio like martin has for example, I personally wouldnt actually want on a road car with big boost, but on a N/A 10K screamer, it would be fantastic.

All about what characteristics you want from your car.

delbee1

I know this is a proper old thread

Just wonder, Harveys 1.78 rod angle, would that be standard bore & crank, longer rods and shorter pistons??

How would Harvey's engine run compared to another engine with the same power but standard rod angle, i.e, what are the advantages?

J1mbo

iTrader: (1)

The advantage of running a better rod angle is to allow the engine to rev more freely. The piston isn't driven into the side of the bore so much.
That engine was a standard stroke standard size bore engine with the longest rod and shortest piston we could get at the time.

I beleive now it's possible to go 141mm rod in a standard deck height block giving a 1.83 but we don't use this.

Ps that engine pulled 9k rpm on the dyno and regularly 8500s in the car!

delbee1

Thanks for the reply

Would that combo give a slightly bigger capacity with the smaller piston size?

I was wondering would you lose torque as a result of the increase in rod size? What were the power figures of the car, if you don't mind me asking, always interested in learning

8500s, bet it went like a rocket, what car was it in and how quick was it?

J1mbo

iTrader: (1)

It was in a group a escort cosworth
It done 0-60 in 2.63 on low boost and 100 in 5.5 on high boost around 600bhp the new engine would have been high fours to 100

Yes a shorter rod does make more torque but it's not a night and day difference IMO

Capacity is original just under 2000 cc and yes it is down on torque in comparrison to stroker engines.

Power figs 613bhp at 31psi and 465lbft useable power was 4000-8500

Martin-Hadland

iTrader: (2)

2.63 is rapid on low boost, how was that recorded?

J1mbo

iTrader: (1)

There was two, one was a 2.7 on low at brunters and a 2.63 at ford fair which I understand is not as accurate as some equipment the low time on low boost came from the traction it was perfect launch. We were aiming for mid 2s to 60 and sub 5 to 100 but never got the chance..

delbee1

That is proper quick, what compression ratio was the car running and was it on race or pump fuel? Also I guess those timings had a lot to do with the car set up, transmission & suspension

Reason for the questions is I'm looking to build or have an engine built for my escort cosworth, you speak to different tuners and get told so many different things with regards to compression ratios etc, seems some get stuck in there ways and others push the boundaries and try new things, some people still are using low comp where others are higher, the people using low say the higher cant be run and will be issues with reliability etc you just feel like lol. Ive been out of the scene for a while and when I had my previous turbo's everything was low compression, since then things have come a very long way, especially with cosy tuning.

Even if I have the engine built I still like to know and understand how it works and what effects it will have on the engine and the way the car drives and runs etc,

Thanks for the replies

SiZT

Though there are other benefits that may or may not affect the engine

Altering the rod ratio would change the c/r I would run (imo)

delbee1

So would you run higher compression with a longer rod angle?

Fiesta_Jed

I would be tempted to go slightly lower.

Mark Shead

I run 8.5 or over for all my big engines. When you put a big turbo on these with a nice exhaust manifold it's easy to use the higher comp.

Mark

delbee1

But what would the rest of the engine spec be? Would you be running lower revs and boost than Harvey's engine

I've been advised by some people to run 7.6/7.7 and say anything more would be unsafe at higher boost

I know compression ratios is an age old discussion, but IMO year on year boundaries are pushed and more power and reliability achievable from the yb engine, I can remember a time when 380 bhp was seen as mega and yet now you can have a reliable 500 bhp car

JamesH

iTrader: (21)

Go with Mark, you won't regret it

Rod-Tarry

8.5 compression ratio -2.8 bar of Boost & 8.8k limit on revs. 838bhp/666ft-lb. This suggests your advice is incorrect as my MAD engine seems to work rather well. The new engine will be better as 5 more years of development will go into it. However this level of engine is very expensive & its always a case of How fast can you afford to go.

Mark Shead

2.5 bar boost and upto 8500rpm depending on cams/hp and turbo used. There is also something coming to sort the block cracking at high power also.

Mark

CossieRich

iTrader: (1)

Mark doesnt know what lower boost levels mean. Not part of his vocabulary

SiZT

All other things being kept the same and if you're already at the point of detonation at crucial parts of the rev range then I would lower c/r when using a higher rod ratio. Unfortunately it's no use saying that low comp is shit or high comp is shit as it's the complete engine build that matters, people have had good results with both. Where people have bad results is when they listen to 5 different people's advise and then build it themselves. Choose 1 tuner/engine builder/whatever they're being called this week and put your trust in their advise and/or service

J1mbo

iTrader: (1)

This was on pump fuel, the faster times we aimed for we're going to be on race fuel.

Compression ratio was no lower that 8.0:1..

We personally range from 7.7-11.5:cr it completely depends on what the engine is for and spec.

Big engines we don't go below standard cr, as mark says turbos manifolds and cams make a huge difference on what cr you can run it's all a juggling game at the end of the day, it's easy to just put an engine together and it work but to get a really well working complete package takes development. Hence the use of a bench dyno IMO is essential.

My own engine spent a week on the dyno playing with cams and I could vary torque from 450 to 490lbft of torque just with timing
I settled at 470lbft and 552bhp as 2wd I didn't want too aggresive and wanted a wide power band

I was keeping it very basic as I didn't want to make an article about it. But as its very interesting understanding piston speeds and dwell etc and their effects go ahead

J1mbo

iTrader: (1)

Sound advise

J1mbo

iTrader: (1)

I hope mark dosnt think I'm talking out of place here but we as companies have two very (IMO) different ideas on engine specs and both companies do very good engines so as SiZT says engines are packages so saying mark runs 8.5:1 and we run 7.9:1 dosnt mean a great deal