Turboing an N/A

[gkcopperdrag]

I've always heard that its not the best thing to turbo a normally aspirated engine. When I ask people why I tend to get different answers though... Some people have said that its because an N/A stock fuel pump can't deliver well enough and the engine will run lean and burn up. Some have said that the engine itsself will literally blow due to the pressure.

Not just the 5sfe, but N/A engines in general why is it not a good idea to turbo them? I'm not looking for a simple "Because they weren't designed for that." What makes them not designed for that? Perhaps on this forum there'll be a consensus or at least a variety of answers which will be debated and/or agreed upon.

Thanks for all and any info

[Piddy]

A big part of it is that turbocharged engines are built with lower compression internals to make up for the extra compression it gets from the turbo charger. Building an NA engine for a turbocharger before you do it is the only way to go. Otherwise you will run into many problems.

[NESW20]

compression. valve timing. tuning. fuel. ignition timing (kind of goes with tuning, i guess). it's much easier to start with an engine that was designed for boost than to attempt to force an n/a engine to handle boost.

-Mike

[Nad1370]

You can turbocharge a N/A engine and still have reliability.

Just as long as you have supporting mods, injectors, fuel pump, ect... and a very conservative tune.

I had a SC Integra GSR boosting 6 psi. Ran 13.70 @ 104 on street tires. # 1 cylinder was down to 80 psi compression. But I got greedy and raised boost to 9 psi.
Engine had 130K miles and half on that mileage was forced fed.

CR on this motor was 10:1

[NESW20]

the 5SFE is somewhat notorious for popping under boost. if you'd like my opinion, get a 3SGTE if you want boost in a MKII MR2.

-Mike

[onehotcamry]

Originally Posted by Nad1370

You can turbocharge a N/A engine and still have reliability.

Just as long as you have supporting mods, injectors, fuel pump, ect... and a very conservative tune.

I had a SC Integra GSR boosting 6 psi. Ran 13.70 @ 104 on street tires. # 1 cylinder was down to 80 psi compression. But I got greedy and raised boost to 9 psi.
Engine had 130K miles and half on that mileage was forced fed.

CR on this motor was 10:1

why are you comparing a gsr motor to a mr2 motor?

With honda it's rather easy to slap a kit on and lay down serious hp. As opposed to our motors, where you have to put serious work into them to lay down big numbers.

[Nad1370]

^^ I'm not comparing the b18 and the 5s. Just sharing my experieces on charging a N/A motor.

If you read the original post. He said " not just the 5sfe but N/A engines in general "

There is no doubt that the b18 has stronger internals than the 5s and has more aftermarket support. But that's another discussion.

You can charge up a 5s engine. But don't expect it to be a dyno queen.
Just a mild 5-6 psi with supporting mods will put a huge smile on the user.

[Piddy]

^ Why don't you have your integra anymore?? Motor blow??

[Nad1370]

Yep .

[Piddy]

I rest my case.....

[quicklsvtec]

I need to post in this I have a N/A MR2 right now here in japan. I am wanting to turbo charge it. It is not the 5s it is the 3s-ge now because the 3s-gte is somewhat the same motor what about putting a turbo on it. I have been looking and right now I think the only kit I can find for it is the Blitz turbo kit. I am thinking about building it all the way from the bottom to the top. Now lets get to the point am I able to transfer parts from the 3s-gte motor to the 3s-ge or are the demensions differnt. IE things like the header, intake manifold, cams, ect.

[gkcopperdrag]

Originally Posted by NESW20

the 5SFE is somewhat notorious for popping under boost. if you'd like my opinion, get a 3SGTE if you want boost in a MKII MR2.

-Mike

This is the type of response I always seem to get. I'm not just talking about the 5s. Are you saying that the engine itself will literally explode from the pressure? May be a silly or stupid question but when you say something made of iron is going to "pop" that's the impression I get.

When you all say the motor will blow is that a literal, or does that mean that something major went wrong and you have to rebuild some of the internals? I'm asking for the details not just the "yeah, it'll blow." Hyde you have any input on this?

Even if I need to take this away from the MR2 lets say the KL03 on an american 2nd gen ford probe GT. 2.5L V6 153hp stock. Lets say we're going to turbo charge that (picking another engine I have so to defer the "don't use a 5sfe, get a 3sgte"). Someone mentioned the compression ratio. Lets say our engine is 10:1 as someone mentioned above; would we need to dip the pistons to drop it down to 9.5:1, or even lower? Is it the actual combustion chamber that can't handle the pressure?

Now lets say that we have our CR down to 9.5:1 (or lower...). NSW20 mentioned fuel. Besides octane ratings for early ignition due to combustion (thanks to Turbos at HowTo for that one ^_^ ), what else are we looking at for fuel. Fuel to Air ratio? Is that different in turbo to non-turbo cars?

Tuning and Ignition: Yeah I can see that... you're supposed to tune and do timing after any real change to the engine.

Also NESW20 I know its easier to start with a motor that's made for a turbo, and I agree with you... but my reason for starting this is to get the actual reasons to "why".

Onehotcamery: What makes the Hondas so easily turbo chargable? Are they built to support it stock (all of the required changes to toyotas mentioned above)?

[Piddy]

Originally Posted by gkcopperdrag

Onehotcamery: What makes the Hondas so easily turbo chargable? Are they built to support it stock (all of the required changes to toyotas mentioned above)?

Because Honda Civic's have a huge aftermarket compared to Camry's.... thats basically why.

[NESW20]

Originally Posted by gkcopperdrag

This is the type of response I always seem to get. I'm not just talking about the 5s. Are you saying that the engine itself will literally explode from the pressure? May be a silly or stupid question but when you say something made of iron is going to "pop" that's the impression I get.

When you all say the motor will blow is that a literal, or does that mean that something major went wrong and you have to rebuild some of the internals? I'm asking for the details not just the "yeah, it'll blow." Hyde you have any input on this?

Even if I need to take this away from the MR2 lets say the KL03 on an american 2nd gen ford probe GT. 2.5L V6 153hp stock. Lets say we're going to turbo charge that (picking another engine I have so to defer the "don't use a 5sfe, get a 3sgte"). Someone mentioned the compression ratio. Lets say our engine is 10:1 as someone mentioned above; would we need to dip the pistons to drop it down to 9.5:1, or even lower? Is it the actual combustion chamber that can't handle the pressure?

Now lets say that we have our CR down to 9.5:1 (or lower...). NSW20 mentioned fuel. Besides octane ratings for early ignition due to combustion (thanks to Turbos at HowTo for that one ^_^ ), what else are we looking at for fuel. Fuel to Air ratio? Is that different in turbo to non-turbo cars?

Tuning and Ignition: Yeah I can see that... you're supposed to tune and do timing after any real change to the engine.

Also NESW20 I know its easier to start with a motor that's made for a turbo, and I agree with you... but my reason for starting this is to get the actual reasons to "why".

Onehotcamery: What makes the Hondas so easily turbo chargable? Are they built to support it stock (all of the required changes to toyotas mentioned above)?

usually what happens is the ring-lands on the pistons break off. ring lands are what support the rings in their grooves. also, detonation melts a hole in the side of the piston, or preignition melts a hole in the center of the piston. sometimes a head gasket will blow.

when this happens, yes, a rebuild is required. many times, due to the extra torque of a boosted engine, the rods and crank need to be replaced. on high-revving n/a engines, the reciprocating assembly (rods, pistons) need to be very light so as not to overstress the crank, which is usually also fairly lightweight. usually, if you're going from n/a --> boost, you replace at least the rods and pistons (pistons for a few reasons).

replacing the pistons gains you a few things: lower CR, forged (strong & light), more skirt clearance (piston skirt to cylinder wall clearance), stronger rings.

usually what can't handle the pressure is the fuel. this causes detonation and preignition, which kills internal components FAST. octane rating is the ability of the fuel to resist ignition from heat and pressure (aka: boost ). this is what usually breaks pistons or pounds out valves and valve seats to the point where they do not seal properly. if you have the right fuel (octane rating), then you can run higher boost (more combustion pressure and temperature).

boosted engines require A LOT more fuel than n/a engines, in general. larger injectors, higher volume/pressure fuel pumps, fuel pressure regulators, fuel rails, very precise fuel control, and tuning. all of these items will help to build reliability into the engine. also, the a/f is different, as you mentioned. in a boosted application, you want to run slightly richer than n/a, since the fuel helps to cool the intake charger and combustion chamber, again helping to prevent preignition/detonation.

i'm sure you already know, but yes, on boosted cars, less timing advance is run, due to octane limitations. another ignition related thing that can help is to run colder spark plugs, since they literally run cooler and help to prevent, at risk of sounding repetitive, preignition and detonation.

as far as ease of boosting hondas, i believe it has more to do with the popularity of the engines and the wide aftermarket support for them. as i'm sure you know, most boosted hondas on stock internals run very low amounts of boost. they usually use a kit from a tuning company that has done all the R&D on the engine and requirements for boost. they address most/all of the issues we've discussed here in a mostly bolt-on package.

one thing toyota did is to put forged crankshafts in many of their engines. the 5SFE crankshaft (back to the 5S, i hope you don't mind ) is actually beefier than the 3SGTE crankshaft. it has larger rod journals than the 3S crank. both are forged. i am actually using a 5SFE crankshaft in my stroker 3SGTE, with aftermarket rods and pistons. for the kind of boost i'm planning on running, i think most honda crankshafts would run and hide.

i hope this helps with any questions you may have. if there's anything else, ask away, i'll try my best to help.

-Mike

[gkcopperdrag]

Awesome reply. Thank you and you answered everything for me. =)