Can i put low comp pistons in a stage 3 2wd cosworth ??

Im running 4 x Greens, 500 intercooler, Breather system, stage 3 Ahmed chip, 4x4 head which is ported and polished, 200 block which is wire rung etc etc

I want around 350 bhp but in future will try to go more.

What would be the best cam and piston combo?

If so which ratio is best? (its all a bit confusing for me)

My engine is out ready for the pistons and cams now so i would appreciate your help

Thanks

 

I would use standard cams for that power.At 330bhp standard comp would be suitable.

My own engine uses 7.6-1 with 2.2 bar,so its not much lower than standard at 8.0-1!

 

To be honest it was for the future, i didnt want to put std stuff in there if in a few months time i want to go a bit further.

What type of engine spec do you have?

What type of pistons are you useing?

Thanks for your reply

 

I have just had my motor rebuilt with 7.2:1 mahles, which will be good for 500bhp, to be safe i would specify this comp ratio to allow for future upgrades.

However be warned, until you run the power through a low comp motor they tend to feel a bit flat, by that i mean between changes when you get back on the power the response isn't as quick as a higher comp motor due to the lower boost levels.

This is worth bearing in mind as if you don't upgrade to big power this can become f***ing annoying !!!

as previous post standard cams should be fine, bd10's don't come into play until 400bhp odd !!!

cheers,

paul

 

What is the difference between 7:2:1 and 7:6:1 and 7:8:1 ??
I know they are different compression ratio but how is it worked out.
I may not want to go for the full 500bhp but in the future push to 400ish,
Does this mean maybe a not so low comp piston would be better.

This may sound like stupid questions to some but im a bit new to all this

Thanks

 

A 7.5:1 ratio will get you to 410 max on light blue inj (near their limit though) above that even lower comp and greys may see you to 450bhp? then 8x 803`s and 7.2:1 for 500bhp+. You could always try a big hit of NOS in your low comp motor? ask around.

 

talk to karl tell him your spec ect he will advise you which way to go and he can live map it for you so it is safe

 

it's always a question of what you ultimately want from the motor.

Like i said before if you go for 7.2:1 you can run 500+ bhp, but the less power you run through a motor with this comp ratio the flatter the motor will feel.

If you are sure you only want a max of 400 odd (ample i would think)!!! then go for a ratio of 7.6:1 and enjoy the hassle free???? motoring of a low comp motor !!!

cheers,

paul

p.s. go for the cosworth racing pistons if you can afford them !!!

 

Thanks every one !!
Alan i will talk to Karl, did you mean Norris Motorsport ?

To be honest i think maybe Paul has got it spot on !! I think 400 will be ok for me to use as a decent track and road toy as the car is used day to day also. I think the 7:6:1 will be the best for me

Would i be able to use a piper fast road cam ??

 

cam ??? you'll need to two !!! only joking

for 400bhp cams will be required bd10's should do the trick, add a pair of vernier pulleys and robert's your fathers brother !!!


paul

 

Thanks Paul

All i needed was a few straight answers ( and a little humour )

For 350bhp are greens ok and would i really need greys for more?

 

Who is the best people to buy the 7:6:1 pistons from?

 

i believe dark greens (803's) begin to struggle at around 380+ so should be fine for 350.

if you wanted more than 350bhp then you could also look at using light blues (403's) before the greys (400's)

as for pistons they don't generally come in a specific comp ratio, you have to get the piston crown machined the the desired ratio that you require.

give paul at pj motorsport a call (01902 862882) he'll give you a good price.

paul

 

Thanks Paul.

Do the machine the std comp Cosworth racing pistons to achive this

 

not sure about the cosworth racing they MAY come machined in certain comp ratios (don't quote me) have a look at graham goode's web site as i think i rememeber seeing cosworth racing pistons advertised already machined.

which ever pistons you go for they will all need machining but you may be able to get them already machined off the shelf as opposed to having to wait a number of weeks !!!


paul

 

Paul what do you mean by this ??

Surely all pistons you buy will go straight in ??

am i being thick?

 

all pistons will fit your block (providing you get the correct size i.e. standard bore +0.5 etc). But in order to acheive the correct comp ratio they will need machining before you put them in your block.

as for the cosworth pistons, i mean that you may be able to get a set straight off the shelf that has already been machined.

whereas with the mahles. you usually just purchase a standard set of 4x4 jobbies, then take them to the machine shop for the work.


hope this helps

paul

 

Ok thanks fella !!

Most machine shops should be able to sort this out then.

Have you had this done?

Any idea on the cost?

 

col karl will sort ya pistons out for ya if you speek to him karl can map grays on standard comp and ya pistons dont have to be pocketed for bd 10s

 

Alan you must be on commission

I will defo try him for a price

Hows ya car coming on ?

p.m me a quick engine spec, just interested

 

alan karl cant LIVE map!

 

Speak to Steve Scott (A1 Rallysport) for low comp Mahle jobbies with valve cut-outs

 

gus yes he can

 

if you go to http://www.cosworth.com and look up pistons it has every type of mahle and cosworth pistons and sizes etc to give u an idea

 

Nice one Toe Knee !!!