Forged piston fuel system question

[Irks]

I'm considering putting in forged pistons for some extra power by upping the compression ratio to 9:1 from 7.8:1. Would any fuel mods be necessary? (besides the upgraded fuel pump of course). I don't plan on having them bored, or anything like that, just want a single drop in replacement to get some extra HP, and to prevent against detonation. Any wiseman input would be appreciated.

 

[rdrkt]

2g pistons are 8:5:1 and they are much better idea for a daily driver. But it still seems like an odd way to go about things. Usually people do the motor last.

 

[Irks]

The real reason I'd like to do this before the normal order of things, is to gain some low end torque (our cars have none), and be able to stick with the stock 14B, or a small 16g. I like the spool of it... What you said still doesn't answer my main question though, which is are fuel system mods (s-afc in particular) necessary to change the piston compression?

 

[rdrkt]

It all depends on your other mods. Increasing the compression a point isn’t all that huge. You will definitely need a fuel pump and a safc and you should be able to go pretty far on your stock injectors.

 

[larryd]

Originally posted by Irks
The real reason I'd like to do this before the normal order of things, is to gain some low end torque (our cars have none), and be able to stick with the stock 14B, or a small 16g. I like the spool of it... What you said still doesn't answer my main question though, which is are fuel system mods (s-afc in particular) necessary to change the piston compression?

no low end torque?? are you serious?? the car has a TON of low end torque compared to most other cars, non v8

 

[Irks]

Originally posted by larryd


no low end torque?? are you serious?? the car has a TON of low end torque compared to most other cars, non v8

You have 8.5:1 pistons in your 98. It's not that these cars have none, but it's just not enough IMO.

 

[larryd]

well i came from a car that had 133ft/lbs of torque at like 8000rpms so anything seems like alot of torque now.

 

[iwantawd]

did you have an old tiburon? that car is the ish!

 

[candela]

No I think larry had a celica... I think they had like 133ft lbs and 180hp stock. It would be cool if it were 133ft lbs @8000 rpm, but I think its around 4600 or so. Anyhow, Irks, I think that if you went with some 2g pistons they would work a little better. The forged pistons wont help prevent against detonation at all, and being higher CR they will actually help induce it with boost. if you tune it right itll hold tons of power and spoolu much faster. 2g pistons are cheaper and arent as high CR as those and will help spool a little. I had all 3 motors almost. I noticed better spoolu with my 2g piston motor, and now Im getting one with forged 9:1. I know a lot of people wonder about this and i will let everyone know how it is. Should be pretty soon now

 

[candela]

Anyhow, if your keeping the 14b, I think an afc and that pump should be adequate for a long while

 

[Irks]

Would the afc be used to richen or lean the mixture? I assume richen, but I'm not really sure.

 

[candela]

Well, you dont have to many mods so dont really expect the afc to d to much. You may benefit from leaning it out and/or richening it up at certain points.

 

[Irks]

So would it be worth it just to do the little tuning I have to do right now, if I were to swap in 2g pistons? I obviously plan on getting it way down the line, but it's an expense I'd like to get away from for now. I figured I'd just lower the boost a little, make my turbo more efficient, and get better gas milage / power.

 

[candela]

I really dont understand what your trying to do here. if you put in 2g pistons it will be fine. You may notice a tiny bit increase in boost response but thats about it. If you want better gas milage then lay off the heavy foot.... boost setting doesnt matter too much ata ll

 

[larryd]

Originally posted by candela
No I think larry had a celica... I think they had like 133ft lbs and 180hp stock. It would be cool if it were 133ft lbs @8000 rpm, but I think its around 4600 or so.

I was closer

Horsepower: 180 hp @ 7,600 rpm
Torque: 130 lb.-ft. @ 6,800 rpm

 

[LaserRST]

I think detonation is an A/F issue more so than compression ratios, so I doubt feul control isnt really necessary, though timing will be different. But as far a boosting, this is where the issue comes to play on higher compression pistons. The whole idea of low compression on turbo cars is to handle boost pressures. Some think that the 7.8 is conservative for the 1gs but actually, like most of the design on this engine, it makes room for more boost pressures than stock. This is why it is so responsive to cheap upgrades, it already has a good race platform. So if you are planning on increasing HP than leave the internals stock, or make the 8.5 max on a street car. If you want the low end and high boost pressures, get the Cyclone dual runner intake, that is the whole reason behind Mitsubishis design of this manifold, is to compensate for the loss on the bottom end. If you want something that is more economical than why not trade it for a NA and add turbo, the cost will even out with some good forged pistons, if you have a good resourse for used turbo parts. My .02$....