Increase Compression

Discussion in '2005+ Ford Mustang v6 4.0L Tech' started by Benwhite911, Sep 11, 2018.

  1. Benwhite911

    Benwhite911 V6'ing & Dealing With It S197 Team Member

    179
    6
    Well, it's about that time again. This V6'er hasn't asked a stupid question in a while so I getting a little restless. If everyone could be so kind as to read the whole post first, then you can all take turns beating the sh*t out of me.

    I've been reading up a little on increasing compression on our 4.0 engines, because I read on the interwebs that that's a way you can increase performance. "Keep Reading" Now, in understand that the traditional method of doing this is through the use of a turbo or super charger to ram more air into the cylinder. I also came across something, of course I can no longer find it, that talked about decreasing the compressible volume as a way on increasing compression. I found that option interesting, as it's most likely to blow up in my face, and I can really only think of one cost effective way to do it. "Almost There"

    The pistons and valves, you can't really change those, unless you change them, and that wouldn't be cost effective. But what about the spark plugs? Is it possible to use a larger spark plug to decrease the compressible volume? When I say larger, I mean the part of the plug that gets screwed into the engine. It's an idea that's been rattling around in my head, so I wanted to put it out there and see if anyone had any thoughs on it. Ok, if you've made it this far, you are now free to do your worst.

    [​IMG]
     
  2. Wes06

    Wes06 forum member

    5,346
    40
    the only way to make it reduce compressible volume, is have it stick out into the chamber, which youd probably wind up smacking the pistons with.

    Correct way is change the pistons
     
    Benwhite911 likes this.
  3. 07gts197

    07gts197 forum member

    718
    25
    Wes nailed it. Besides increasing compression doesnt produce much power. Every full point of compression raised is worth about 10 hp, not worth it.
     
    Benwhite911 likes this.
  4. CammedS197

    CammedS197 forum member

    577
    31
    Thinner head gasket is another option. But that doesn't do a whole lot. Maybe .1 to .3 compression depending on the OEM thickness. But like said above that nailed it.
     
    Benwhite911 likes this.
  5. LarryJM

    LarryJM forum member

    189
    6
    I read a Chrysler report years ago on the Cross Rams that were offered in the late 50s and early 60's It was like 8 to 9 compression was worth 15% and 9 to 10 was 8% and 10 to 11 was 4% and 11 to 12 was 2% and 12 to 13 was 1%. They offered the Max Wedge in both 11.5 and 13.5 CR. One was 415hp and the other was 425. Then I know for sure a 8 MPG 70RR 9.5CR Magnum Cam 383 with 3.91 gears would not run on 29.9 cent reg gas.
     
    Benwhite911 likes this.
  6. Gab

    Gab Bullitthead

    67
    7
    While your thinking is correct (a larger plug will reduce combustion chamber volume), it isn't practical for another reason besides contact with the piston and/or valves: spark plug location isn't arbitrary, and it's location is determined for optimum combustion based on several factors (air/fuel mix, swirl, etc.).
     
    Benwhite911 likes this.
  7. Benwhite911

    Benwhite911 V6'ing & Dealing With It S197 Team Member

    179
    6
    Thank you all for your input on this. I have the say, that was relatively painless, as I as expecting a thorough A$$ Whoopin. I'll get back to hypothesisizen new performance ideas, and I'm open to suggestions too. So feel free to get thinkin, and remember, there are no bad ideas.

    [​IMG]
     
  8. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

    36,996
    462
    I knew I'd be sorry opening this thread... I wasn't disappointed.
     
    Hawgman and Benwhite911 like this.
  9. Throck!

    Throck! Junior Member

    1
    0
    Shave the heads.
    Get in touch with an engine builder to learn what compression that engine can handle first.
     
  10. massacre

    massacre Junior Member

    5
    1
    Well I don’t know if it would work on a SOHC v6 or not, but a head swap might do what you are asking.

    On the 4.6 sohc V8 there were 2 versions.
    Early version had slightly dished pistons and a large combustion chamber.
    Later versions had pistons with more dish, and a smaller combustion chamber.
    So you can install the small chambered heads on the smaller dished pistons and increase compression. Think it is a point/point and a half.

    On the 4.0 OHV V6 there is the same situation- where early design used small dish/big chamber and later used big dish/small chamber so again, a head swap would increase compression about a point.

    Obviously you would need to know which pistons you already have, if you have the big dish on the piston this won’t work. Big dish + big chamber means your compression will decrease. Which could be helpful in a boosted situation.

    I have no idea though on the 4.0 sohc I will have to look into that
     
    Benwhite911 likes this.
  11. smartass_garage

    smartass_garage Junior Member

    21
    2
    The Sport Trac flex fuel 4.0 has higher compression heads to deal with the different fuel.
    I have a Sport Trac flex fuel 4.0 in my Mustang, I put it in after blowing up my original engine when the timing components took a shit. I put all new (cloyes) timing components on the replacement (Sport Trac) engine as well.

    Here's a video of my dyno pulls with it. Stock mustang flywheel hp is 210, I'm making 211 at the wheels with what I have done (mod list is at the end of the video).

     
    Last edited: Nov 8, 2018
  12. Benwhite911

    Benwhite911 V6'ing & Dealing With It S197 Team Member

    179
    6
    Pretty nice. Thanks.
     
  13. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

    8,513
    160
    smartass_garage likes this.
  14. Benwhite911

    Benwhite911 V6'ing & Dealing With It S197 Team Member

    179
    6
    I'm sure there's a logical explanation, but because I don't know, I just have to ask. Why does a Supercharged Intake need an intercooler?
     
    smartass_garage likes this.
  15. Wes06

    Wes06 forum member

    5,346
    40
    you compress air, you heat it. You heat air, you get less power out of it due to reasons.

    you want the air compressed, AND cold
     
    smartass_garage likes this.
  16. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

    8,513
    160
    Yup when you compress it, it makes it hotter. That makes the ECU pull timing. That costs power. The intercooler takes the heat out of the compressed air which allows proper timing to still be used.
     
    smartass_garage likes this.
  17. Benwhite911

    Benwhite911 V6'ing & Dealing With It S197 Team Member

    179
    6
    Nice, thanks all. I knew there was a reason.
     
  18. smartass_garage

    smartass_garage Junior Member

    21
    2
    No one that I know of makes turbo kits for the 4.0 anymore.

    All the supercharger kits are very very expensive, you can buy a used coyote for the price of a supercharger kit. The m90 kit is the cheapest option but m90's don't really make all that much power.

    Also if you plan on making that much power, your rear end needs to be swapped to an 8.8. The stock v6 rear ends are garbage. I put an 8.8 with 3.73's in and it made a world of difference

    It's basically not worth throwing that much money at a 4.0 in my opinion, the 3.7 is a different story.

    I don't plan on putting any more effort or money into my 4.0, I have a LS3 that I'm going to put in the car because I want to v8 swap and can't really afford a coyote.
     
    Last edited: Nov 14, 2018
  19. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

    8,513
    160
    I will be cheaper in the end to buy a V8 car than V8 swap a car you have. Sell what you have take what you plan to spend on swapping and you have a GT.
     
    smartass_garage likes this.
  20. Benwhite911

    Benwhite911 V6'ing & Dealing With It S197 Team Member

    179
    6
    I know I need to stop chasing V8 performance with my six, and just do a swap already. And this will sound stupid, but for emotional reasons, I have to keep the car I have.