ross piston compression help

[churcherj]

ive just taken out the pistons and rods i bought, and have emailed ross and have said the flat top pistons i have have a ratio of 9:5:1 or lower? what is stock compression, as this seems quite high? im planning to run a td04 at 1.4 bar but im unsure of the compression ratios and i need to inform the engineering firm..will be using a 1.2mm headgasket, can anyone confirm if this would be ok?

 

[J25GTi]

That's higher than stock, I'm not sure about the headgasket though. You would want a slightly higher than std compression ratio for a really responsive ride

It is the way forward!

 

[churcherj]

That's higher than stock, I'm not sure about the headgasket though. You would want a slightly higher than std compression ratio for a really responsive ride

It is the way forward!

ok mate sounds good, i was under the assumption lower compression is better for higher boost? but will run cack off boost?

 

[J25GTi]

Its all about compromise, the lower the compression the more boost you can run, but its a lazy drive.

Higher compression, slightly less boost, but its more responsive, and will come in harder and earlier

 

[churcherj]

Its all about compromise, the lower the compression the more boost you can run, but its a lazy drive.

Higher compression, slightly less boost, but its more responsive, and will come in harder and earlier

ok mate thanks for the info rep'd...now need to see if the new ross piston rings need to be filed down or gapped?

 

[thefalls]

You could always go with the stock compression ratio and thats responsive enough.
Or you can use a thicker head gasket to lower the compression a bit.

 

[thefalls]

That will need to be checked with a feeler gauge but prior to that you will have to calculate the clearance that is needed depending on your set up,nos or strip or street use.
The wiseco spec sheet gives you an idea,but ross will have their own specs.

 

[350ep70gr]

ive just taken out the pistons and rods i bought, and have emailed ross and have said the flat top pistons i have have a ratio of 9:5:1 or lower? what is stock compression, as this seems quite high? im planning to run a td04 at 1.4 bar but im unsure of the compression ratios and i need to inform the engineering firm..will be using a 1.2mm headgasket, can anyone confirm if this would be ok?

LoL..email ross and tell them that chris said you dont know what you doing..LOL It is obvious that you speak with a regular guy and noone with some experience.
Any flat top piston on a 4e engine cant give more than 8,3 cr WITHOUT CALCULATING the gasket thickness AT ALL.
1330 cc /4 =332,5 cc per cylinder /39 cc volume of the chamber = 8,5CR . Add the gasket you want,deck height,first ring height and you go even lower than 8,5.
Are you sure they havent reply for a 5e setup?
Anyway for 1,4 bar on a 4e you need a cr very close to stock 8,2. Do your calculation to find out what hg you need to bring the cr around this number.

Chris

 

[churcherj]

LoL..email ross and tell them that chris said you dont know what you doing..LOL It is obvious that you speak with a regular guy and noone with some experience.
Any flat top piston on a 4e engine cant give more than 8,3 cr WITHOUT CALCULATING the gasket thickness AT ALL.
1330 cc /4 =332,5 cc per cylinder /39 cc volume of the chamber = 8,5CR . Add the gasket you want,deck height,first ring height and you go even lower than 8,5.
Are you sure they havent reply for a 5e setup?
Anyway for 1,4 bar on a 4e you need a cr very close to stock 8,2. Do your calculation to find out what hg you need to bring the cr around this number.

Chris

hello mate, hes quoted for a 4e setup, im dealing with ian? he also recommended a piston to bore clearance of 0.004" and the manual recommends 0.006" so im abit confused tbh! seem to be getting mixed replies, and afterall ross are meant to know this information

 

[350ep70gr]

hello mate, hes quoted for a 4e setup, im dealing with ian? he also recommended a piston to bore clearance of 0.004" and the manual recommends 0.006" so im abit confused tbh! seem to be getting mixed replies, and afterall ross are meant to know this information

I tell you that 9.5 from a flat top piston on a 4e is not achivable unless you have the intension to do it..(like reshape chambers etc)On a standard engine it is a big NO. Apart from that about clearence i dont really want to say what i use as dont want people to follow my advice and blame me afterwards if something go terrible wrong...What i can say is that i have built one with the clearence that ross give for turbocharge aplications (0.006)or something and the owner used it all the time with 70hp shot of nitrus (till the engine died from oil starvation on the last bearing). According to ross we need to have add 0.002 or something for the nitrus application wich obvious we didnt (as it was suposed to see 1- 1.2 bar from a tdo5-16g max). After opening the engine we come to the conclusion that the suggested clearence was very generus...Thats why to other builts mine included i go for tighter clearences than recomended. (On my personal one you hardly notice it has forgies inside even on dead cold).
Dont follow my way...just do what your builder recomends as he will have the responsibility..

Edit: Ross should have a cr calculator on their web page (on the technical section)..fill the numbers and see yourshelf if it is possible the 9,5 cr.

Chris

 

[thefalls]

Thats some good advice.

 

[churcherj]

I tell you that 9.5 from a flat top piston on a 4e is not achivable unless you have the intension to do it..(like reshape chambers etc)On a standard engine it is a big NO. Apart from that about clearence i dont really want to say what i use as dont want people to follow my advice and blame me afterwards if something go terrible wrong...What i can say is that i have built one with the clearence that ross give for turbocharge aplications (0.006)or something and the owner used it all the time with 70hp shot of nitrus (till the engine died from oil starvation on the last bearing). According to ross we need to have add 0.002 or something for the nitrus application wich obvious we didnt (as it was suposed to see 1- 1.2 bar from a tdo5-16g max). After opening the engine we come to the conclusion that the suggested clearence was very generus...Thats why to other builts mine included i go for tighter clearences than recomended. (On my personal one you hardly notice it has forgies inside even on dead cold).
Dont follow my way...just do what your builder recomends as he will have the responsibility..

Edit: Ross should have a cr calculator on their web page (on the technical section)..fill the numbers and see yourshelf if it is possible the 9,5 cr.

Chris

u legend chris cheers for the info im going to do my slighter tighter than 0.006, will go for ross's suggestion of 0.004, have also heard aswell chris that similar ross piston users have gone for a tighter clearance with no issues

 

[350ep70gr]

u legend chris cheers for the info im going to do my slighter tighter than 0.006, will go for ross's suggestion of 0.004, have also heard aswell chris that similar ross piston users have gone for a tighter clearance with no issues

Cheers mate! More than happy to help and share my experience! Go with the ross recomendation tho.... and do the midle from 004 and 006..

Chris

 

[churcherj]

Cheers mate! More than happy to help and share my experience! Go with the ross recomendation tho.... and do the midle from 004 and 006..

Chris

0.005 it is then have heard people using 0.0045 with good results but cant really see it making much difference tbh, will get it done to 0.005 and see how we go

 

[thefalls]

As Chris has said,when you go for tighter clearance then you wont even know if the engine has got forgies when cold.
I couldnt believe it when i heard such an engine and its been 2 years already since being built.
Still sound!

 

[weeJohn]

I run the same pistons as you with a 1.2mm head gasket, i have ran 1.4 bar for a few years and had some gasket failures on stock head bolts. I went to a 2mm gasket to lower the CR and save my gaskets but at the loss of a little power.

I went back to a 1.2mm gasket and fitted ARP head bolts, my problems with gaskets have been solved so I would recommend you using them.

 

[churcherj]

I run the same pistons as you with a 1.2mm head gasket, i have ran 1.4 bar for a few years and had some gasket failures on stock head bolts. I went to a 2mm gasket to lower the CR and save my gaskets but at the loss of a little power.

I went back to a 1.2mm gasket and fitted ARP head bolts, my problems with gaskets have been solved so I would recommend you using them.

hi mate thanks for the info u running a td04? i will be using ARP headbolts so hopefully that will sove that issue, i would go for 1.4mm but i dont want it to run crap off boost, want to keep some responsiveness, rep'd

 

[weeJohn]

hi mate thanks for the info u running a td04? i will be using ARP headbolts so hopefully that will sove that issue, i would go for 1.4mm but i dont want it to run crap off boost, want to keep some responsiveness, rep'd

I hit full boost at 4200rpm in every gear, its a TD04HL so slighlty bigger than the Imprezza units. I tried going from a 1.2mm to 1.4mm and didnt really notice any difference, I was using a Blitz active ECU at the time so cant say if timing was altered after the change.

If you use the ARP bolts I would say you wont have any problems with a 1.2mm gasket, unless you get a lot skimmed off the head and deck.