'86 300zx in need of at least 400hp(stock now)

[longlivetheZ]

Ok...here we go...I confirmed my thoughts in the Forced Induction forum before posting this.

Raising the boost = raising cylinder pressure with air and fuel.
Raising compression = raising cylinder pressure with metal (decreasing cylinder size in some way...piston shape, combustion chamer shape, whatever).

What would YOU rather have...a cylinder full of metal (metal's heavy!!) or a cylinder full of air/fuel mix? *Runs out to buy lower compression ratio pistons...*

Originally Posted by k3

i actually looked into this a few years back...if you took the VG30DE and built it stronger with much stronger pieces. you could actually run the stock 8-9psi that the TT does and make 500rwhp+.

Sure, it is a bit of a give and take but it comes down to reliability...how reliable a car are you looking for? Sure...top fuel guys probably do run 184:.2 compression ratios and 77psi or whatever, but they can do that...they rebuild at least part of their engines every 2 or 3 races. You wanna rebuild your engine once or twice a month? I don't. I'll lower the compression ratio a little and pack in more air and fuel instead.

Originally Posted by k3

example: lets take the turbo off of the 7.8:1 compression ratioed VG30ET and dyno it. it will have less HP than the N/A motor because the compression is 1.2:1 lower.

Of course...but if you strap a turbo running 6-7 psi onto a VG30E, you'll greatly sacrifice durability. I don't believe anyone would argue with what either of us are saying. We're both right...we just kinda have different takes on it. Both are doable.

Originally Posted by k3

like i said, it is a teeter-totter effect. this is why there is no engine from the factory that comes with a VERY low compression. because ti doesnt help matters...

if you wanted to increase performance you would build the motor stronger and higher the compression. now you have a motor making alot of power and boost on top of that.

It is a give and take...what you seem to not really take into consideration is the reliability aspect of it. Sure there are engines being produced with low compression ratios...they have turbos or S/Cs strapped to them. Why do you think manufacturers lower the compression ratios when adding forced induction to an engine? Because they can't have their cars blowing up all over the place. Yea, a 2.3L 4 banger with an 11:1 comp ratio and a turbo pushing 14 psi would be a SCREAMER...but only for about 2 miles, if that...get my point?

[k3smostwanted]

i undersatnd the reliabilty...but this is when i look back at the statement that started this.

"the bottom end with no mods is supposidloy able to hold 700 hp but to do that you still need to lower comkp. "

lowering the compression wil not allow you to acheive miracles. yes it will help reliabilty and making the engine less like to ping/detonate, but the fact of the matter is that lowering the compression down too much will only hurt your peformance. there is a certain point that you dont want to cross. the less N/A compression...the longer it is going to get power to the turbo to help spool it. once spooled the boost can take over and the engine can only help.

lowering the compression any lower than the stock 7.8psi is assinine and it will not benefit the performance of the car.

if you want to make your car more reliable than what it is already from the factory. by all means, lower your compression but you will lack the performance. if you want to built a 700hp engine, you will need to make the engine stronger and keep it at 7.8:1 compression ratio so it can handle more boost but the engine itself still produces the same or more power.

you will not sacrifice reliablity by making the engine stronger but keeping the same compression ratio.

if you think that lowering the compression is the answer to making power out of a turbocharged car then i would talk to every turbocharged car modifier and ask them why they are not running a 2:1 compression ratio.

im sorry to get a little agitated...its just i feel that lowering the compression to an engine is not the answer unless you start with a 10.5:1 compressioned Naturally Aspirated motor.

teh key to performance is to get the compression as close to the physical maximum as possible without sacrificing the engines ability to last more than a few hours.

[ExTrEmEDrIfT]

ok i know this is completely off subject and im sorry but i forget --- what the hell does ( i.e. ) stand for?? kinda dumb quiestion but im having one of those stupid moments lol

[longlivetheZ]

i.e. is a latin abbreviation meaning id est or, "that is". It's a more professional way of saying ex for an example or whatever.

K3...you seem to mis understand me and think I'm talking about lowering the compression a TON. I don't mean that. I mean lower it enough to be able to run enough boost to meet your requirements. If you can run stock comp and run forced induction AND meet your goals without it blowing up in 5 min, go for it. If you're rebuilding everything, then lowering the compression is more likely to be unnecessary. It is a happy median...you have to lower it some if you're going to be running really high boost, but you can't lower it too much or you'll be shooting yourself in the foot...again...it's a give and take.

It's kinda like getting an aftermarket exhaust...you have to have back pressure but not too much. 2" is too small and isn't very effective, but 3" is too big and you start to lose low end torque...so 2.5" is perfect.

What you're talking about is making a turbo charged NA engine...adding a turbo to a higher compression engine is essentially this. Would it work? It should. It's like all the small block Chevys out there that basically had turbos slapped onto them. They run relatively low boost, but retain the stock compression. It doesn't really matter much...either way...

And I DID ask a bunch of turbo guys...everyone in the Forced Induction forum...I gave you the link...

[k3smostwanted]

Originally Posted by longlivetheZ

i.e. is a latin abbreviation meaning id est or, "that is". It's a more professional way of saying ex for an example or whatever.

K3...you seem to mis understand me and think I'm talking about lowering the compression a TON. I don't mean that. I mean lower it enough to be able to run enough boost to meet your requirements. If you can run stock comp and run forced induction AND meet your goals without it blowing up in 5 min, go for it. If you're rebuilding everything, then lowering the compression is more likely to be unnecessary. It is a happy median...you have to lower it some if you're going to be running really high boost, but you can't lower it too much or you'll be shooting yourself in the foot...again...it's a give and take.

It's kinda like getting an aftermarket exhaust...you have to have back pressure but not too much. 2" is too small and isn't very effective, but 3" is too big and you start to lose low end torque...so 2.5" is perfect.

What you're talking about is making a turbo charged NA engine...adding a turbo to a higher compression engine is essentially this. Would it work? It should. It's like all the small block Chevys out there that basically had turbos slapped onto them. They run relatively low boost, but retain the stock compression. It doesn't really matter much...either way...

And I DID ask a bunch of turbo guys...everyone in the Forced Induction forum...I gave you the link...

well you simply left it at...lowering the compression will benefit because it will be less metal and more air.

by that statement it soudns like the lower you lower the compression, you can fill that void with air and it will equal the same compression. yeah that might work....but how are you gonna get the air in there without proper means.

im telling you that it would be assinine to lower the compression any lower than the 7.8 psi to make it perform better. the more you lower the compression, the mroe turbo lag you will have and the more air the turbo has to push. which means...a bigger turbo which will make your turbo lag even worse than before.

i think Automobile Engineers know what the proper compression ratio should be to have a good balance of reliability strength and performance. why change something that takes months and years od engineering because you as a tuner think it wil work better? i think they know a little more.

you take a car and build it by lowering the compressiona dn whatever else. and ill take a car and and just build the engine stronger to handle more boost. then tell me who will have more power and a better power band.

It is a happy median...you have to lower it some if you're going to be running really high boost,

but if you keep the compression at the same thing...you wont need to run as much boost to get the same power because the motor will also be making power of its own.

it's a give and take.

exactly what i have been saying...but i guess i have misunderstood you because it seemed to me that you were speaking of lowering the compression to help performance. in which case i understood that since lowering the compression helps performance...why not go all teh way and go as low as you can get. but that wouldnt work...because you will lose power. I admit...you could probably get away with lowering the compression some on the VG30ET and be ok....but why do that just so you can raise the boost a few psi to make up for it. so now by lowering the compression...you are making the engine less powerful so it will take longer to spool that same sized turbo but once spooled it will need to create a little more psi. that is assinine...

if i were to properly build a VG30ET motor....i would raise the compression to 8.5:1 with much stronger bits...that way i can make more power without running more boost. the higher compression will make the engine more powerful so when i go to upgrade to a bigger turbo...i will be able to pick out soemthing that meets me flow needs and my engine will still spool it.

[stephenp]

2 to 1 compresion and 75 psi boost wow hold the fuck on
use a miniture exhaust turbine and a hella huge intake turbine now theres some numbers to crunch and guess what thats on 87 you get like somewhere near 100 psi off of 93 so add in the 2 mile theory and some HIGH octane gas and you get like 200 psi of boost and some where in the neiborhood of the same horse as the saturn space shuttle

but on the real note
i stated to lower comp. ok so i also said do it through the head clean it up and unshroud the valves youll be somewhere between 7.2 and 7.5 to 1 comp. ratio
ok add oversized valves and port and polish (hand lapped shit
coat the pisons or just polish them to a mirror your choice
get some bigg inj. and a hybrid turbo that spools quickly deliveres high boost numbers and has a external waste gate or what ever there called that releases the excess exhaust gasses
get a aftermarket ign. stand alone if able to
get non resistor type plugs and aftermarket coil
radical asymetrical cams, springs, titanium retainers ect
and the oil squirters are placed under the pistons mounted to the block and squirt oil directly at the bottom of the pistons to help aid in cooling of the pistons
a windage try and crank scrapper on a oversized 8 qt oil pan with high volume pump and high pressure springs
yes its also a good idea to have the crank, rods, and rockers balanced and polished for lightweight valvetrain components and the ability to use a lighter valve spring for less wear, friction, and more power etc
modified intake might help
intercooler is a must
aftermarket clutch, flywheel, driveshaft, maybe some internals for the tranny and differential fior longevity


on the note of why change (lower comp) something ewnginmeers blahh blahh blahh
hello more power different standards they gave you reliability a little bit of power and at a good price and they could mass produce these thingsa and make money and have happy customers


ok well anyway if the guy is serous and have cash i can give very specific answers but when he is as vague as to sday i need 400 hp and im stock now........

you want win one race where either of you have less than 1000 into your cars or do you want to have it a few years and drive it reliably with 10,000 cash or is money no object you gottas be more specific also thanks for the boost forum site thing i gotta check that out and pic some brainms

[longlivetheZ]

Engineers didn't design the engine for what we're using it for. It's that simple. If you change the way you're going to be using something, the design must change accordingly.

[stephenp]

quite similar to what i stated... ??? were you agreeing.....
also on the note of the exhaust that was stated before
someone stated that 2 was too small and 3 was too big annnnt wrong answer he's boosted run 5" ehaust out behind the front tire through the fender and guess what only gains more
turbo = backpressure
also 400 hp on 2 1\2"??????? cfm flows arent great enough for a 2 1\2" straigt pipe to handle 450 hp so do the math too restrictive for 400 hp
on a stock motor yeah the 2.5 will work fine with manderel bends but when modding alot of the time bigger isnt only better but a necessity


also if your poor but have 1500 and want 400 hp get a hybrid turbo i taslked about some 555cc inj and a 100 shot of nos for the spool, and a high pressure and volume fuel pump and your good to go

but then you sacrifice every thing from emissions to idle quality tio longevity you name it but you get 400++++ hp

[k3smostwanted]

Originally Posted by longlivetheZ

Engineers didn't design the engine for what we're using it for. It's that simple. If you change the way you're going to be using something, the design must change accordingly.

but they do indeed design to be reliable but powerful...most tuners want their engine to be powerful but still reliable so why change. just upgrade it...

i dont see the point of lowering the compression just so you can higher the boost to make up for it. when all you have to do is make the engine stronger so it can handle more boost...

if i were to do anything to the Z31's compression...i would build it stronger and utilize the 8.5:1 compression ratio of the Z32TT. then you will have a much stronger and powerful engine but still reliable...and you wont have to run as much boost to get the same power.

if it was such a good idea to lower the compression ratio of a turbocharged car...it makes me wonder why i have never seen it done. we have such Z's that the owners have spent over $20k and owners like Ash who are pure genious' and your telling me nobody has thought of lowering the compression ratio to get more power out of the Z's, Supras, VR4's, or any other car for that matter. i think it has been thought about and has been discarded due to the teeter-totter effect and that effect making it a waste of time and can only hurt performance in the long run. the lower you lower the compression the last power the engine is going to have to spool the turbo.

[longlivetheZ]

Originally Posted by stephenp

quite similar to what i stated... ??? were you agreeing.....
also on the note of the exhaust that was stated before
someone stated that 2 was too small and 3 was too big annnnt wrong answer he's boosted run 5" ehaust out behind the front tire through the fender and guess what only gains more
turbo = backpressure
also 400 hp on 2 1\2"??????? cfm flows arent great enough for a 2 1\2" straigt pipe to handle 450 hp so do the math too restrictive for 400 hp
on a stock motor yeah the 2.5 will work fine with manderel bends but when modding alot of the time bigger isnt only better but a necessity

I didn't mean that literally...it was just an example. There's no way I'd wanna run 2.5" exhaust on 400 hp car with a turbo.

Originally Posted by k3

i dont see the point of lowering the compression just so you can higher the boost to make up for it. when all you have to do is make the engine stronger so it can handle more boost...

Cuz it's cheaper and easier to swap in a little thicker head gasket to lower compression than it is to buy new rods, pistons, crank, and so on.

Originally Posted by K3

if it was such a good idea to lower the compression ratio of a turbocharged car...it makes me wonder why i have never seen it done.

You may not see this because people usually mod turbo engines that came from the factory with a lower compression ratio and a turbo. Therefore, they don't need to do anything further in this area.

This all has been info as best as I could explain it. I have contacted Gale Banks Engineering (Sure...you've...heard...of...them...them, right? The guy's a turbo MASTER.) with the question in hopes SOMEONE would be able to cast some light on the subject. I'll let you know what happens.

[k3smostwanted]

Originally Posted by longlivetheZ

You may not see this because people usually mod turbo engines that came from the factory with a lower compression ratio and a turbo. Therefore, they don't need to do anything further in this area.

This all has been info as best as I could explain it. I have contacted Gale Banks Engineering (Sure...you've...heard...of...them...them, right? The guy's a turbo MASTER.) with the question in hopes SOMEONE would be able to cast some light on the subject. I'll let you know what happens.

ahh....as we just discussed on AIM....we were on 2 different pages. i thought you were siggesting that lowering the stock 7.8:1 compression ratio on the Z31T would net you greater performance. i know you will want to lower the compression ratio on most N/A motors. though the Z31 N/A has a ratio of 9:1 which isnt all that bad for forced induction. its just the fact that ARP's will be needed to make sure everything doesnt fly apart.

[DeleriousZ]

wow so i'm finding a turbo diesel that will fit in my z... lol

[longlivetheZ]

lol, D. I'd like to get a T-diesel to play with.

Yea...almost what I was looking for.

"Improved Intercooler Airflow
The Z has pretty good intercooler air flow management in stock trim, with molded plastic ducts directing the airflow from vents in the front bumper to the intercooler. With the big intercoolers, these ducts do not fit anymore and the intercoolers have to depend on random air coming through the bumper vents. This really hurts the efficiency of the intercoolers (even though they are still much better than stock)."

What they're referring to is the 2 Stillen units they used in the stock locations...dunno why I thought they used an FMIC. Still think I read somewhere that an FMIC is better, though...lol...

[k3smostwanted]

Originally Posted by longlivetheZ

What they're referring to is the 2 Stillen units they used in the stock locations...dunno why I thought they used an FMIC. Still think I read somewhere that an FMIC is better, though...lol...

told ya...the stillen side mounts are the best flowing intercoolers for the Z32. it is people like wagz creating over the Hp that the sidemounts can handle that need to go with a front mount, otherwise...sidemounts are the best performers for the Z32.

so yeah....i will be going with some Stillen Side mounts and a CO2 custom injection for each one this winter if everything goes as planned. s:

[DeleriousZ]

think you can fit a boost cooler system in there somewhere too?