motor

sergei_dekker85 · 02-13-2005, 01:32 AM

any ideas on how to change the compression ratio W/O changing pistons,crankshafts and valves??

ZfrkS62 · 02-13-2005, 01:34 AM

thinner head gasket is the first thing that comes to mind. you could always try decking the head or swapping heads with a different year with a higher C.R.

sergei_dekker85 · 02-13-2005, 01:38 AM

Well My Engine is a QR25DE....relatively new engine to the market(same one used in the B15 sentra SER spec-V) plan to change it to 11.3:1 currently running it at 8.9:1 what about grinding the block? heard of it?

ZfrkS62 · 02-13-2005, 01:52 AM

if you're going to do that, you need to be royally carefull not to overheat. it won't take much to warp your block once you start decking. and if you're going to do that, you may as well change your crank since you'll have to disassemble the engine to send the block and head to the machine shop. (CNC machining locates the cylinder bores off the main journals)
you can't change compression as much as you want to with out changing either the crank or the pistons.

T-Bird · 02-13-2005, 02:09 AM

Originally Posted by sergei_dekker85

Well My Engine is a QR25DE....relatively new engine to the market(same one used in the B15 sentra SER spec-V) plan to change it to 11.3:1 currently running it at 8.9:1 what about grinding the block? heard of it?

well that's kind of what he meant by the decking the heads. You have to make sure if you do any of this that it wont cause the valves to hit the cylinders which can cause some major problems. so yes you could take some metal off the block and or heads and a thinner gasket but going up that high of compression without replacing any large components doesn't sound like a cheap or easy job.

lev_p · 02-13-2005, 02:50 AM

First, for greater compression ratio you grind off the head, not the block. Have it made by specialists, otherwise you may grind too much or not even. You may also need to reprogramm engine's ECU, or get another one. When you are at it, have also some porting done - doesn't cost much, but makes some improvements.
After you do that, use only the best fuel (highest octane ratio) you find - otherwise it'll detonate.
Me and a lot of my friends have done it on our cars - and now 12 year old French cars drive like mad

P.S. You might need to have a new head gasket custom-made from thin stainless steel...

sergei_dekker85 · 02-13-2005, 04:09 AM

Hmm...ot bad eh...11.5:1 ratio SUV....

Best way in my country 2 gain power W/O getting into trouble with the law (TCing and SCing is illegal in my country FYI)

ZfrkS62 · 02-13-2005, 04:13 AM

(TCing and SCing is illegal in my country FYI)

that's gotta be the dumbest thing i've heard since finding out norway gives out fines for modded mopeds

T-Bird · 02-13-2005, 05:01 AM

Originally Posted by lev_p

First, for greater compression ratio you grind off the head, not the block. Have it made by specialists, otherwise you may grind too much or not even. You may also need to reprogramm engine's ECU, or get another one. When you are at it, have also some porting done - doesn't cost much, but makes some improvements.
After you do that, use only the best fuel (highest octane ratio) you find - otherwise it'll detonate.
Me and a lot of my friends have done it on our cars - and now 12 year old French cars drive like mad

P.S. You might need to have a new head gasket custom-made from thin stainless steel...

Not always the case on some head designs you cannot take very much off of them or you will affect the width of the cylinder and the fact that some have such low clearance heads in order to save room it would be quicker and easier to deck the block. You rarely would have to change the computer for compression ratio changes since there are no sensors for compression ratio last time I checked. And last time I checked if you take your heads to a proper machine shop porting isn't cheap maybe in Israel but here it is expensive if you can't do it yourself. See personally if I couldn't SC or TC my car I would pull the heads and the oil pan and CAREFULLY change the crank and pistons, upgrade the fuel injectors and rails upgrade the ignition, possibly change all the valve train components and cams themselves. POrting is nice if you can do it yourself but I've only seen it really effective in a forced induction setting. Decking the heads and or block has some potential problems as listed above with over heating but I wouldn't worry too much about detonation because if you don't change the actual shape of the head there shouldn't be any new hot spots.

ZfrkS62 · 02-13-2005, 05:30 AM

There are other ways to make power other than compression. Fuel is one of the better ways, thats where the injectors come in. RPM is the other way. If you balanced the engine and destroked it, you could spin a couple thousand more RPM.

My ex-boss has a civic that spins 13,000. Just by balancing

but by deboring/stroking a 327 to a 286, the guys in the shop next to us got a 67 Nova to launch at 12 grand, shift at 11 and redline at 13. and this is a V8

so before you go running around to find out who will do the best job for the least amount of cash at shaving off a couple thousanths of metal...i'd look into stroke and bore changes.

sergei_dekker85 · 02-13-2005, 06:18 AM

Originally Posted by ZfrkS62

There are other ways to make power other than compression. Fuel is one of the better ways, thats where the injectors come in. RPM is the other way. If you balanced the engine and destroked it, you could spin a couple thousand more RPM.

My ex-boss has a civic that spins 13,000. Just by balancing

but by deboring/stroking a 327 to a 286, the guys in the shop next to us got a 67 Nova to launch at 12 grand, shift at 11 and redline at 13. and this is a V8

so before you go running around to find out who will do the best job for the least amount of cash at shaving off a couple thousanths of metal...i'd look into stroke and bore changes.

well too bad thats illegal here and that'll fail inspection tests....

sergei_dekker85 · 02-13-2005, 06:21 AM

Originally Posted by ZfrkS62

(TCing and SCing is illegal in my country FYI)

that's gotta be the dumbest thing i've heard since finding out norway gives out fines for modded mopeds

believe it or not yes...saying that "will compromise the structual integerity of the veh and will compromise on emissions"....wtf well if u'd want to u'd have to go thru alot of paperwork...getting the blueprint of the model of the TC or SC that u're fitting and a confirmation letter from the car manufacturer that this model is safe for fitting into this veh. and will not effect the veh in emission standards and safety...what a pile of CRAP

sergei_dekker85 · 02-13-2005, 06:23 AM

heres the link to my country's yes and nos of mods :http://www.onemotoring.com.sg/publis...ion_guide.html

get this...NOS is not allowed too

ZfrkS62 · 02-13-2005, 06:26 AM

well too bad thats illegal here and that'll fail inspection tests....

what do they do? disassemble the engine and measure everything

:shock:

believe it or not yes...saying that "will compromise the structual integerity of the veh and will compromise on emissions"....wtf well if u'd want to u'd have to go thru alot of paperwork...getting the blueprint of the model of the TC or SC that u're fitting and a confirmation letter from the car manufacturer that this model is safe for fitting into this veh. and will not effect the veh in emission standards and safety...what a pile of CRAP

so i take it a twin turbo supra is non existant there? note to self: do not move to singapore

sergei_dekker85 · 02-13-2005, 08:20 AM

Originally Posted by ZfrkS62

well too bad thats illegal here and that'll fail inspection tests....

what do they do? disassemble the engine and measure everything

:shock:

believe it or not yes...saying that "will compromise the structual integerity of the veh and will compromise on emissions"....wtf well if u'd want to u'd have to go thru alot of paperwork...getting the blueprint of the model of the TC or SC that u're fitting and a confirmation letter from the car manufacturer that this model is safe for fitting into this veh. and will not effect the veh in emission standards and safety...what a pile of CRAP

so i take it a twin turbo supra is non existant there? note to self: do not move to singapore

NONONO...what it means that If yr car is Naturally aspirated its illegal to be TCed or SCed....but if a car comes Stock with a TC or a SC then if u wanna change it to a better one its allowed