stock efi block

Looking at doing a remote turbo on my 94 efi 300. Tuning would be through megasquirt.

I'm looking at how much boost it could handle in stock form before I can build a better block.

Also wondering what kind of power I could make if I go gotta route with a mild cam that will keep my low end and maybe a little port matching on the head.

The main problem is detonation.
You will be working with cast pistons and a 8.8:1 compression ratio so you will have to be conservative.
If you can control the ignition timing and air/fuel ratio you can get away with 6 to 8 lbs of boost.

The amount of intercooling is the other very important part of the system.
The more heat you can pull out of the air after the turbocharger, the less chance for detonation.

Keep the stock cam for now because it has a lot longer advertised duration than the aftermarket cams and will help with the higher EFI compression ratio of 8.8

The next block you build can have a lower compression ratio and a matching cam specifically for turbocharging in the rpm range you intend to operate at.

What rpm range power band are you looking for?

I figured that's about what I'd be looking at. All is want from a cam would be another 1000 usable rpms.

What could I expect as far as power with that kind of boost on an otherwise nearly stock engine?

Expect around 40% increase in torque with 6 to 7 lbs of boost depending on the amount of intercooling.

Turbocharging will normally increase the upper rpm range of the power band without changes.

When it comes time for the new block, if you want low rpm power for heavy duty use keep the intake duration near 200*
Something like a 200/192 .050" duration cam with a 114 degree lobe separation angle combined with high velocity head work will give you good power to 4500 rpm.

You will need an 8:1 compression ratio.

That's not bad, I had hoped to eventually see the 5-600 tq range with some usable power band so I can run more gear and still cruise on the highway. I'll be turning 35-37" tires so gobs of torque and some gear would make it a beast.

jarryd2018":qmn30v6o said:

That's not bad, I had hoped to eventually see the 5-600 tq range with some usable power band so I can run more gear and still cruise on the highway. I'll be turning 35-37" tires so gobs of torque and some gear would make it a beast.

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For 500 ft.lbs of torque at 3500 rpm you will need a ported head that will give you a 90% volumetric efficiency.
With that head, 12 psi of boost will give you just over 500 ft.lbs and 16 psi upwards of 575 ft.lbs.

It will be much easier to get an 8:1 compression ratio using the carburetor head with 76cc chambers.
The pistons will need a 32cc dish if they are ideally set at zero deck height.

If the EFI head is used the piston dish will need to be over 40cc.

Try to find a low mileage block that needs very little overbore. You will want the thickest cylinder walls possible.
I would also have the block sonic checked for core shift.

Go ahead and spend the time and money on your ignition system - ditch the TFI. If you run TFI then you are limited to a minimum of +10 deg timing, this is what will limit you to 8psi. The swap to EDIS will allow you to go down to -10deg timing.

I converted to EDIS after using TFI for a few years - well worth the effort. Be prepared to pull a lot of timing as you go past 10psi, my unprepped EFI head will knock at 4 deg and 12psi on 93octane.

Turbo_B":3c6zamyp said:

Go ahead and spend the time and money on your ignition system - ditch the TFI. If you run TFI then you are limited to a minimum of +10 deg timing, this is what will limit you to 8psi. The swap to EDIS will allow you to go down to -10deg timing.

I converted to EDIS after using TFI for a few years - well worth the effort. Be prepared to pull a lot of timing as you go past 10psi, my unprepped EFI head will knock at 4 deg and 12psi on 93octane.

Click to expand...

I would use an msd6a or control the ignition with the megasquirt.

I'll be starting out with low boost on the stock engine and then I'll build a new one with low compression, ported head, forged goodies etc. I'll hopefully have the boost by the end of the year and the new engine and more body by the end of next year. The timeline all depends on if I get a promotion or not.

When you run EDIS do you use coil packs or some form of COP? I'm trying to figure out how that would mount up, haven't seen it done.

This link to a site members EDIS install may give you some ideas on using the coil packs, enjoy.

viewtopic.php?f=7&t=67718

I probably won't go to EDIS until after I build a new engine. I think I'd be pretty content for a while on low boosand I can take my time building a new engine.