Forged Piston-sizes

[ArmRS]

Hi guys. I would like to apply forged pistons to my MK1 172 and wrote to Accralite about that. They say that they need the diameter of the pistons and valve pocket sizes. Do you know the sizes I need to give them to produce? I have Schrick 288 degrees camshafts and superchips modded ECU fitted. Do you think I can get away with it by just changing the pistons or do you think that I have to change some more parts to make the engine more reliable?

Any of you guys fitted camshafts other than originals and also pistons??

Thanks...

 

[BUTRE]

Dont know about the pistons size of the 172, but arent they the same size of the willy ones?

why do you want forged pistons?? more rpm and want the pistons to handle? would the crank handle more rpm? turbo/supercharging?

 

[BenR]

Whats wrong with the std pistons?

If your only changing the cam (to no benefit, std profile is fine and you wont gain any bhp, but you will loose torque) then you need not worry.....your not putting any extra stress on any parts.

Easiest way for you to find out piston size and details is to have a look at yours. but they are 87.2mm.........depending on the cam profile, you might want to check if you can deepen the pockets.

 

[PaulRobo]

thats gonna be well expensive, if your going to all the expense of forged pistons it must be some mad wild plan you have in mind. It sounds to me like you have to much money, or at lease more than sesne (no offence)

 

[ArmRS]

The point is that one of my pistons have just melted and the piston holder (dont know the meaning in English exactly, might be wrong name) broke into melted pieces. That is why I need stronger pistons and holders to handle. However havent thought about the crank, wouldnt the original crank handle?

I dont agree that the camshafts I put are useless, the response of the engine at higher revs is much better with these camshafts. I confirmed this by trying the car with my friends cars which I had tried before as well.On the other hand, Schrick claimed an increase of 15-20HP.

Anyway what happened was as it had superchips, I revved it till 7800RPM and then pulled to 3rd gear but the piston and its holder just melted. I thought that what I could do about this problem would be to use forged components. Or maybe it just happened because it was 78000RPM, I am not sure. I dont want same thing happen once more after the new engine is installed.

 

[ArmRS]

Accralite wrote to me that I could get pistons from them for 105 pounds per piston. That is not so much I dont think. On the other hand they will be used in drag races so my sponsors will pay for them (hopefully )

 

[BUTRE]

so its all about handling more rpm.

I would check some other parts as well. Crank and valve springs. Need to know if std crank wont vibrate too much at higher rpm and if the valve springs are up to the task of closing the valves in time...
dont want no valve crush when piston goes to TDC.

Cant fine no where on the web about F4R engine parts spec.

 

[ArmRS]

Thanks mate anyway, I will try the Renault dealer here.

So you think that it is the RPMs that melted my piston. On the other hand what I have been thinking about is why more RPM is better. Apparently there is no need to rev till 7800RPMs as the peak bhp is given in 6400RPM with superchips and when I talked to guys in Schrick, they said that the torque/BHP curve would be similar to the original one but with a change in peak BHP raised 200RPMs above, to 6600RPM (They told me this when I asked them whether superchips ECu program is suitable with their camshafts). So I think if I rev it till, lets say 7300-7400(When the shift change light appears after superchips) it will be the best choise.

 

[Fred@BTM]

melted piston??? do you have an indution kit K+N or Pipercross etc?????

 

[ArmRS]

Forgot to write that I asked Schrick about the valve springs and valves and they told me that ther is no need and they dont produce for Clio RS anyway. They said that the originals would be adequate to cope with the stress after their camshaft. But I am not sure whether they are right or wrong... I also once checked about the crank, I found one in USA, the price was $4500, so I backed off

 

[ArmRS]

I have put a Green filter (which is not to suit the original one, I mean the filter of an induction kit) that I installed in the place of the original filter.

 

[Fred@BTM]

So you have just a green filter inside the original airbox??? Reason i ask, is because induction kits and 172 engines dont really mix too well!!!! In other words they normally mess up the fueling causing the engine to run lean = metled pistons

 

[ArmRS]

Quote: Originally posted by Fred2001Dynamic on 01 May 2003

So you have just a green filter inside the original airbox??? Reason i ask, is because induction kits and 172 engines dont really mix too well!!!! In other words they normally mess up the fueling causing the engine to run lean = metled pistons

Yes that is right. However Ive had it for last 40000kms. Do you think the reason might be the filter, isnt it a bit late?? If so, it would be a very small detail causing a huge problem.

 

[BenR]

Oh well, your piston melting is NOT a result of RPM....its a result of ignition and fueling that combine to create either detonation which breaks a whole in the piston or your exhaust temps are too high.

Did you check the fueling?

Sounds to me that you melted a piston through poor fueling.

The std crankand flywheel are not the best balanced assembly and you could do with a nice session on a dynamic balancer.

By piston holder im assuming your talking about the gudgeon pin?

As for the camshaft....std one is good for 215bhp........the problem is the throttle body, its too small. Your near the finite amount of air you can apss anyway, so using a wilder cam will do nothing but move the powerband up and loose you torque.......if they quote 20bhp...hold them to it, get them to agree that the cams make that much, fit them and get it tested (on the same day and with the same parameters) if it fails to....you get a refund........easy. Far too many people willing to believe out there!

 

[ArmRS]

Quote: Originally posted by BenR on 01 May 2003


Oh well, your piston melting is NOT a result of RPM....its a result of ignition and fueling that combine to create either detonation which breaks a whole in the piston or your exhaust temps are too high.

Did you check the fueling?

Sounds to me that you melted a piston through poor fueling.

The std crankand flywheel are not the best balanced assembly and you could do with a nice session on a dynamic balancer.

By piston holder im assuming your talking about the gudgeon pin?

As for the camshaft....std one is good for 215bhp........the problem is the throttle body, its too small. Your near the finite amount of air you can apss anyway, so using a wilder cam will do nothing but move the powerband up and loose you torque.......if they quote 20bhp...hold them to it, get them to agree that the cams make that much, fit them and get it tested (on the same day and with the same parameters) if it fails to....you get a refund........easy. Far too many people willing to believe out there!

Unfortunately I dont have my 172 yet, but I will install the camshafts and try it on roling road when the car is out. I think the name of parts I mentioned were conrods, I mean the linkage between crank and piston. That is melted and its in 100 pieces.

Do you mean that camshaft kits dont work at all or is it only for 172s because of the throttle body. My friend has a 206 GTI and after applying just superchips and kentcams camshafts he was able to pass CTR in a drag. It is also true for 106 GTIs, a fried of mine has a 106 GTI, he has full supersprint exhaust, K&N induction kit, superchips, port polish and 280degrees camshaft, he can pass M3s and standart Imprezas in a drag. On the other hand, as far as I know, when you have a better intake manifold, surely it is better performance wise but what does it have to do with the camshafts?? I mean when the valves are open for a longer period doesnt it mean that the amount of air intaken is increased?

How do I check the fuelling?? The fuel pressure was supposed to be OK when I checked it last time. Apart from that I was just gonna clean the injectors but the engine broke down. Do you think that I have to apply a FSE fuel regulator or just get rid of the Green filter ad apply a original sized Green one, or just clean the injectors as it has 87000KMs on the clock.

 

[BenR]

oh dear, looks like we need a complete re-programming of the brain here! lol

The conrods, if they melted and there is evidence of melting then you had some MAJOR problems! if its jsut twisted/shattered i think you were looking at severe detonation as this has the same effect as hitting the top of a rising piston with a sledge hammer.

Im not saying the cam wont do anything, but in your present setup.....it wont. Sure, the longer the valves are open, essentially the more power you can make, but you also need rpm to make use of that extra duration, as you wont make any more power than 86%-100% VE in the normal rev range.

And to get more air in the cylinders, you need to have an non restrictive induction system, and that means your filter, throttle body/ies and manifold. The std one is about the size as one off a 160bhp civic VTI!!!

So, add more duration, youll just move the power band up as your limited to a finite amount of air on your std throttle body. What does the inlet system have to do with the camshaft.....well, if you can only flow 200cu.ft/min and to make the power your wanting you need 350cu.ft/min then your basically stuchken!

The head is where all the power is "stored" the cams you use and the throttble bodies/mapping is all an attemp to take as much out of starage as possible. Cams dont make power, its easier to think of them as items which allocate and dictate where and in what quantities the power will be made. You could have a 500bhp engine, but slap on a induction system that can only physically make 200....and well......you know.

Everything is inter-twinned with eachother, the bolt on and tally up system really doesnt work. As for Checking the fueling, get yerself on a gas analyser, wide band lambda (specialist equipment) and a Rolling Rd to check and sort anything that needs to be.

You really shouldnt be twisting a rod and melting a piston with basic and bolt on mods!!!

As for the Pugs, im quite involved with the 206 scene in HK and to say that you CANNOT make much power on the std inlet system as its more restrictive than our 172s! lol.......on the std cam you can make 160bhp with a modified 406 inlet manifold and TB. So changing cams WILL NOT be resulting in CTR beating.....yet alone the 106!!!!