Forged Pistons.

[Guest]

Ok, the engine is out, so I may as well drop my CR and fit forged rods ready for some boost.

I have decided on Carillo Rods, but am stuck on what Pistons to use. It seems the two top choices are JE or CP? 9:1 or 10:1?

Thoughts anyone?? I like to get opinions from experienced users before diving in.

I'm thinking I should go for 10:1 CP?

[Lauren 2259]

It depends upon how much boost you want to run. The lower the compression the higher the boost, but I guess you are going to get more lag if you're going for a big turbo. 

[Mark@Abbey M/S 235]

Turbo or SC?

 

Running stock squish area in the cylinder head?

[Guest]

Lauren, I intend to go the Turbo route and am looking at lower CR more for safety than anything. We constantly read about our friends across the pond making silly horsepower on stock engines, but for how long??

Mark, I intend to go The Turbo route. As for the squish, I can't recall what it looks like on the FA20, but I do remember it looks weird from pics I've seen. I am also a little suspect of the massive inlet ports which look big enough to feed 1000hp??

Having seen an engine stripped down, I remember it raised a lot of "Why did they do that" questions. It's not as plain and simple as an RB26 eh!!

[Special K 442]

Horses for courses, Nige... is it to be a weekend racer or just an extremely fast road car...?

 

Adrian is pulling 420+bhp on standard rods/pistons at 1.1bar boost, on 9:1 c/r you could be looking at a potential 550bhp on 2.0bar.. mebbe a bit more on the right fuel..

 

Either way, you will need to consider larger injectors, hi-flo fuel pump, oil cooler/deep sump, I suggest. And a diff oil cooler should not be ignored if you're looking for sustained trackday use..

 

I think Lauren's lag concerns can be mainly overcome by astute mapping. Mark at Abbey has knowledge of building/developing LFA's l/c engine, so is well worth listening to.. the new ver.4 AVO turbo from Adrian looks good for the upper horspower figures..

 

... then there's the Cosworth conversion to consider... if and when it makes the starting blocks..

 

Spec K

[Lauren 2259]

I guess it begs the question, do you want to make silly horsepower? What are you aiming for in this respect?

[Special K 442]

Aww c'mon, Lauren.... who doesn't want to burn off a Porsche 911T on the road....?

 

:ph34r: :ph34r:

 

(I see that Rollcentre Racing have got their 24hr Britcar GT86 up for sale.... hmmm....)

 

 

Spock...

[Lauren 2259]

Aww c'mon, Lauren.... who doesn't want to burn off a Porsche 911T on the road....?

..

 

In a straightline, I don't. 

[Guest]

Horses for courses, Nige... is it to be a weekend racer or just an extremely fast road car...?

 

Adrian is pulling 420+bhp on standard rods/pistons at 1.1bar boost, on 9:1 c/r you could be looking at a potential 550bhp on 2.0bar.. mebbe a bit more on the right fuel..

 

Either way, you will need to consider larger injectors, hi-flo fuel pump, oil cooler/deep sump, I suggest. And a diff oil cooler should not be ignored if you're looking for sustained trackday use..

 

I think Lauren's lag concerns can be mainly overcome by astute mapping. Mark at Abbey has knowledge of building/developing LFA's l/c engine, so is well worth listening to.. the new ver.4 AVO turbo from Adrian looks good for the upper horspower figures..

 

... then there's the Cosworth conversion to consider... if and when it makes the starting blocks..

 

Spec K

 

I'm not sure that Adrian is running standard 12.5:1 CR is he??

 

As for the question regarding how much power i want? i think 400HP for now is adequate. I'm being more cautious than anything with lower CR and forged rods and pistons.

 

I think 10:1 will be my choice, but which pistons have the best reputation for these engines??

[GT86Jay 202]

Adrian is running stock internals including stock 12.5:1 CR.

 

All Adrian has changed are the injectors and fuel pump. 

[Kodename47 446]

Lets not forget that Adrian does run race fuel (108 RON?) which is a massive safety net for the CR too to make those figures.

 

Also worth noting that alot of the Americans quote WHP so those running ~350whp will be about your 400 goals. Steveoexige's car is running decent power from a non-AVO setup and is still on the original internals IMO, although I don't think he's had his on a dyno yet.

[Guest]

Adrian is running stock internals including stock 12.5:1 CR.

 

All Adrian has changed are the injectors and fuel pump. 

 

That's incredible !! It must be on the limit now??

[GT86Jay 202]

That's incredible !! It must be on the limit now??

 

I'm sure. 

 

What is 'on the limit'? No body really knows how far these engines will go. 

 

Is on the limit 1 bar that lasts 50k miles. Or is on the limit 2 bar that lasts 10k miles? 

 

The Fensport race car engine will be going forged for next year though. And they are going to examine and closley inspect this years engine to see if its done any damage or how it looks. 

 

Personally i'd be following what Costworth are looking at CR wise. 

[Special K 442]

I agree with Jay on this - Cosworth are talking about supplying  just the internal bits for self-build or a new short block.... the standard (nitrided) crank is well up for increased power but if you're considering much more than Adrian's running at present a billet crank must be a better bet.

 

I've done 30k miles on the standard stuff and, if I go forged with upped boost, I will definitely look at a new crank.

 

It's a pity that Cosworth are proving so unreliable in regards to availability.

 

Spec K

[Special K 442]

Steve - Steveoexige is going forged over the winter, I believe.

 

Spec K

[Guest]

When I say "on the limit" I mean just about ready to self destruct/ melt Pistons/ blow head gaskets, that kind of thing.

I think we'll find that Cosworth will use another brand of rod/ piston. It's just knowing which one?

As for new cranks, I recently watched an EJ rebuild video on YouTube that stated a new crank cost like $350!!! Cheap!!

[Mark@Abbey M/S 235]

Race fuel will always  help detonation is the killer of these motor nears the limit running a race fuel will help this.

 

Running low compression with 98 fuel helps as well as it helps again with detonation issues.

 

Working on the Squish helps detonation control , when you see Detonation the main issue is the increased cylinder pressure which will over load the engine components. Normally remvoiing sharp edges , removing the squish totally will help a lot and not effect the way the car runs at off boost.

 

Cylinder pressure is the main item that will break parts , big boost @ big rpm isn't normally an issue but big boost at low RPM is the killer due to the amount of time the motor is at peak cylinder pressure.

 

You can map around this issue with a turbo car by tapering the boost pressure and working the cams to give the car less dynamic compression around the area you are worried about cylinder pressure where as a SC car never makes full boost unless the car is at maximum RPM.

 

any further questions ask away.

[Guest]

Thanks for this very knowledgable input Mark. I have been led to believe a turbo charged engine actually cushions the compression cycle, acting like a damper almost? Obviously this only applies at sensible boost levels.

When you say "big boost at low RPM", what figures are we talking Mark? I once had a friend who bent a rod on a T5 Volvo running big boost. This happened at very low RPM.

So Mark, what Pistons do "you" recommend?

[Mark@Abbey M/S 235]

Hows does a charged car cushion the compression cycle?

 

Fi forces air into the cylinder so running over 100% Volumetric efficiency so you can add more fuel and make a bigger bang , bigger bang normally means more Torque=more BHP

 

 

A turbo car will make boost at a lower rpm as it works on exhaust flow not the RPM at what the SC is being spun at , so at lowish RPM with a big load (high gear) a turbo car will make full boost as the RPM is low the motor is at Peak cylinder pressure for longer so can hurt the motor easier like your friends T5 did.

 

 

bent conrod from high cylinder pressure.

 

We use CP pistons with good results, plenty of other makes out there

[Guest]

Thanks Mark, once again.

Go on tell us all, how did the bent rod in the picture happen?

I have an old American publication regarding turbocharging engines. It goes into the why and why nots of AM turbo's and states that having a charge forced into the cylinder actually softens the load reversal on the rod and piston... that's how I read it anyway, but then, I'm getting old and forgetful now.. so probably have it wrong lol!!

What are your views on the massive inlet ports on this engine? They look big enough to feed a cylinder twice the size to me??

You know, Mark, you are talking me out of big boost with a Turbo now.. It looks like I could be playing with fire because I know sod all about mapping? I've had three R32 GTR's, which all had issues, in fact you bought the interior out of one of them!!

[Mark@Abbey M/S 235]

Nigel,

 

 

Stock Piston crown, we see a lot of sharp edges that can start detonation but a car running Direct Injection needs a piston to help swirl that is why the crowns look like they do , just looking for some pictures of the CP piston we are using at the moment.

 

you don't need big boost being a 100bhp per litre NA motor already it breaths very well so doesnt need a lot of boost to make some really good power thats why big inlet ports really work well when FI a NA motor.

 

I would go for a large turbo spec to stop the turbo spooling hard at lower rpm so softening the spool of the turbo this will allow the boost to be controlled with the throttle easily not like small responsive blower where you lift off and the turbo still makes boost.

 

I can understand that being FI helps at the top of the stroke as the piston has some load going over TDC but the killer on the conrod is under compression not extension.

 

another GT86 owners coming from a GTR. I think the GT86/BRZ will be a cult car like the GTR models (32/33/34)

[Guest]

OK, so the decision has been made.. carillo Rods and CP pistons.. now I need to decide on CR. 9:1 will be good for big boost, 10:1 not so good, but will retain some off boost driveability I guess? also, the 10:1 will have room to go down a bit on CR when "cleaning up" the crown and chamber.

 

If I set myself a target of 420HP tops on Optimax I guess 10:1 will be OK? Basically I will sacrifice a little top end power for extra safety. Theres also the issue with those direct injector seals to consider into the equation? I guess big boost and risk of knocking will kill them?

 

In my world, I would like to build the engine with lower CR and still have driveability whilst I decide where to go with my FI plans...

 

Dya know, the more I write, the more I realise I need more advice from a pro than I thought lol!!

 

On the subject of ports, I have a friend who is pretty hot with heads and tells me the ports are way too big airspeed through the port will be too slow. he also claims that FI will exasperate the situation. I would have thought port shape would not be as critical on a FI application?? 

[Mark@Abbey M/S 235]

Nigel,

 

 I would go for 10.1 compression ratio;

 

 Yes agree slight work on the combustion area will lower the comp ratio a little more;

 

 I tend to disagree about the Port size thou , I think there was a lot of money poured into the development of this motor making good power , the torque dip is a pain but we can help that issue with a tune. With regards when FI bigger is better I feel  thats why engines like the FA20/VQ35DE/VQ35HR and the VHR37 go so well with some boost pushed up them they flow really well.

[Guest]

Thanks for the advice on CR Mark. Perhaps you'd like to quote me happy for a set of CP Pistons and Carillo Rods?

Perhaps I should be looking at ARP head studs as well? While we're on the subject, I see no mention of good quality bearings in all the mod posts?