I've never been a fan of F/I but after seeing a few turbocharged EPs, its got me contemplating over it. Idealy, I would like to swap a k20a2 and charge it because I would start off with a better motor, but what i've heard is that its not good to charge it because it already runs at a high 11:1 compression. What I've seen a lot of people do is swap the type s head and use the k20a3 block since it runs at a lower compression. It would be cheaper for the k20a3 + type s head swap and then charging it but money really isnt an issue. Anybody experienced with turbos please help me out!

 

You can run a turbo with that higher compression but your margin for error will be less and your tuner will really have to know what he or she is doing.

 

and would they all have the same boost potential? I know jack **** about turbos so please enlighten me. Could both engines run the same lbs of boost or is it that the higher compression engine cannot handle as much?

 

Again, it is in the tuning, internals, etc. LB per LB of boost a higher compression engine will make more HP than a lower compression engine, but again, the more boost you run on a higher compression engine, the less room there is for error. Someone correct me here if I am wrong, I believe you could run the a lot of boost on a BUILT high compression engine, by built I mean pistons, rods, sleeves the whole nine yards, but again the margin of error is lower.

 

lower compression is probably a better option for you if you are new to the game.

sam

 

Lots of professionals (not talking import scene) run high compression and boost. I've seen engines running 14:1 and 8lbs of boost on '91 pump gas (that's the most aggresive I've personally witnessed on pump gas). Again the secret is tuneing. Higher compression engines are more prone to knock. Since the compression is high the result is that at TDC the air/fuel mixture is heating due to an adiabatic compression process (as the gas is being compress very little energy is transfering to the surroundings requireing that the energy show itself as heat). So the likelyhood of the air/fuel mixture igniting spontaneously before the spark plug fires is high. To compensate for this there is a couple of things to do. First is to look at cooling. The hotter the engine, the hotter the charge will be. Adequate cooling systems and intercooing is a must. Next is to look at fuel. It's important to remember that fuel makes power not air. All the air is doing is helping to burn more of the fuel. People tend to guage injector size on boost level when they should be baseing it on fuel pressure and more importantly horsepower and torque. While most people run 550cc injectors on their street setups from what I've seen I feel that on a high compression turbo engine 720cc injectors will allow you enough playing room. Also remember that high horsepower engines (300+hp range) aren't economical on fuel. Run a/f ratios probably in the 10.5-12.5 range and richen the injector duty cycle (or whatever variable you're using to tune the injectors) by 5-10% for street driven applications as the quality of gas can vary drasticly. Finally you'll want to tune the ignition timing. Here a good knock sensor is a must and an EGT guage can help. To extract the most power you'll want to advance ignition timing to the brink of knock then back it off 2-4 degrees (possibly more).

As you've possibly guessed I wouldn't even attempt this setup without a standalone or Hondata bare minimum. Linear FPR's are a must. Upgraded fuel pump.

Now the engine will have to be sleeved but I wouldn't close it up with a blockguard. For one you're gonna need as much cooling as possible of the cylinder walls, especially at the top of the cylinder where the air/fuel mixture is most volatile. Second if you're filling a cylinder with close to 2 atmosphere's of pressure then compressing it, there is a chance for the cylinder to distort with the piston only a 1/4 of the way through the compression stroke. However, at 8-12psi the cylinder pressure will not be increaseing exponentially till the piston is near the top of the stroke. As a result the headgasket will be a weak point but the likelyhood of a ductile iron cylinder flexing significantly near TDC is small. Your failure point will be the head gasket (which is alot cheaper to replace). Now you will be making significant power so I'd suggest crower rods. Again your rods should suit your power level. Stock Honda rods are way too tiny to support the kind of power a turbocharged motor will put out. As for pistons I say stick with what works. It depends on the engine you're talking about but for a B16A2 I'd use JDM ITR pistons which should place the motor around 11:1 for a C/R. For one I think that Honda has really good piston design. The skirts are teflon coated, they're light weight and will give you the C/R you need.

Now I don't suggest you do this unless you really know what you're doing. Also I don't think there is any import only shop in the US that I'd trust to tune this motor correctly. If you can't tune it then you'll need to take it to a shop that works on racecars (ALMS, KART, NASCAR, IRL, etc.) to tune the engine. Expect to spend alot of money too. You've got to pay to play and when it comes to cars the only way to make up for experience and knowledge is with money.

So yes it can be done. It has been done. It does work. It is fast. But if you're not scientifically and mathematically inclined why not just take the money, save up and buy a faster car?

 

So yes it can be done. It has been done. It does work. It is fast. But if you're not scientifically and mathematically inclined why not just take the money, save up and buy a faster car?

You know, if more people thought like you, we would have allot less "my motor is making a funny noise" threads floating around honda-tech

Rob

 

I personally like lower compression turbo motors. Why? Because you have more cylinder volume to utalize when the piston is at TDC. You can cram more air and fuel into the larger volume of a low compression motor at TDC. It makes a lower displacment motor "act" like it has more displacement. THe downside is you have to be comftorable running lots of boost. You also have to design the system to be efficient at elevated boost pressures. In the end you can only run so much dynamic compression. You can raise the static compression and run low boost. Or you can run low static compression and raise to boost to reach the dynamic compression limits.

 

i agree with danl......

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RexSiT3 &raquo;</TD></TR><TR><TD CLASS="quote">i agree with danl......</TD></TR></TABLE>

Me to ]

I love low compression and running 20psi on pump gas!

Brian

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danl &raquo;</TD></TR><TR><TD CLASS="quote">I personally like lower compression turbo motors. Why? Because you have more cylinder volume to utalize when the piston is at TDC. You can cram more air and fuel into the larger volume of a low compression motor at TDC. It makes a lower displacment motor "act" like it has more displacement. THe downside is you have to be comftorable running lots of boost. You also have to design the system to be efficient at elevated boost pressures. In the end you can only run so much dynamic compression. You can raise the static compression and run low boost. Or you can run low static compression and raise to boost to reach the dynamic compression limits. </TD></TR></TABLE>

great explanation!

 

Thank you all for the help.

 

Originally I was going with 10:1 compression on my new built motor. I then decided 9.2:1 will be a better choice for me since I am on shitty 91 octane gas.

The reason I wanted 10:1 was for more responsive street driving, faster turbo spool, not having to run as much boost to make my power which = lower intake temps.

Then I decided to see the light and realize I might as well just up the boost, run more timing to make up for lost power, feel safer with a wider margin for error on lower octane, and brag about how many pounds I am running.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MiraiZ &raquo;</TD></TR><TR><TD CLASS="quote">

great explanation! </TD></TR></TABLE>

Man, I usually confuse the hell out of people.

 

I'm partial to 10:1, and I wouldn't personally run higher than that. When the day comes that I have to rebuild this motor, I will probably stick with 10:1.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danl &raquo;</TD></TR><TR><TD CLASS="quote">I personally like lower compression turbo motors. Why? Because you have more cylinder volume to utalize when the piston is at TDC. You can cram more air and fuel into the larger volume of a low compression motor at TDC. It makes a lower displacment motor "act" like it has more displacement. THe downside is you have to be comftorable running lots of boost. You also have to design the system to be efficient at elevated boost pressures. In the end you can only run so much dynamic compression. You can raise the static compression and run low boost. Or you can run low static compression and raise to boost to reach the dynamic compression limits. </TD></TR></TABLE>

great explanation!

 

ill be usign srp 10.5:1 and crower forged rods on my d16 and boost arround 13-14psi... ill use a thick head gasket to bring it down to arround 10:1

im doing this because i got a punny tdo4 and dotn want to put more money into a bigger turbo so raising the static compression will yield comparable results as using 9.1:1 and some 18-20 psi ... less lag also

tunned with aem ems and by a guy that build and tunes race cars..

im debatign on usign my Y5 head (roller rockers) or gettign a Y8 head...
ill be tunnign with stock internals tomorrow and have fun with it while i build a botom end. i wanan see hwo torky the hx head is compared to the y8

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kamaleon &raquo;</TD></TR><TR><TD CLASS="quote">

im doing this because i got a punny tdo4 and dotn want to put more money into a bigger turbo so raising the static compression will yield comparable results as using 9.1:1 and some 18-20 psi ... less lag also

</TD></TR></TABLE>

Thats fine and all, but to make horsepower you need to flow air. I don't care how thermodynamically efficient you make your motor by raising the static compression. You will not make a tdo4 flow efficiently even at low boost levels at the higher airflow levels.

 

what about a t25 with 10.6:1 Je pistons on a gsr runing less than 10 psi daily, is that safe? sorry to jack your thread but i think it fits nicely in here