Project MIDTRBO

[SappySE107]

Still doesn't make sense to me. It would make more power with less boost with the original stroke. You have to boost it more to get that power, so how does that help?

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[ALLTRBO]

Dave96z34 is only seeing one small piece of my puzzle, that's only one small piece.

Less off-boost torque, and overall torque. Not as much less hp.

There are the reasons other than power that I mentioned above as well.

[Joseph Upson]

Dave96z34 is only seeing one small piece of my puzzle, that's only one small piece.

Less off-boost torque, and overall torque. Not as much less hp.

There are the reasons other than power that I mentioned above as well.

Unless you are more interested in the sound of the engine at unusually high rpm I agree you should not destroke the engine for the following reasons:

Torque is what makes a turbo car fun to drive.
Even with boost until you push a high level of pressure, offline shock torque is not going to equate to the getrag crushing V8 torque and if you don't abuse the transmission from the start it will hold up well.
The V6 doesn't have a well documented history of breaking transmissions the way the V8 in a Fiero does and there are quite a few turbo Fieros.
You've already stated you will consider the F23 transmission if there is a problem so it would be better to build the engine to its max and see what the results are rather than reduce the displacement and then turn around and boost it back up to compensate and you will turn up the boost and keep turning it up until something stops you.

I've done the turbo Fiero several times, even going as low as a 1.8L turbo Sunbird motor despite being warned that the torque level would be too low for the fun factor. I disregarded the warning and wound up doing it over later with a V6. Redoing gets old very, very, fast.

What Sappy is expressing is the essence of turbocharging, making the most power on the smallest amount of boost. If you are that worried about the transmission holding up, build the engine at its stock stroke and turn the boost down, that won't cost you anything.

Just my advice from experience.

[ALLTRBO]

Thanks for your advice as well. I know you and the others have considerable 60V6 experience, and I appreciate the comments and advice. I'm not trying to shrug you guys off by doing it my way, I'm just trying to explain why I'm doing it my way.

I do want the sound of an 'unusually high rpm' 60*.

I only half agree about the torque. It isn't the torque that makes a turbo car fun to drive, it's the method of torque delivery. I like the feeling of being slammed back into the seat when the boost kicks in. Either setup will deliver this plenty well enough. 'Fun' is subjective anyway, really. Some won't touch anything except a smooth powerband from a well built N/A car.

While I haven't done a turbo Fiero before this, I've gone the turbo DSM route going from a bone stock 15-second car all the way through (14's, 13's, 12's) to a high 11-second AWD street rocket. You absolutely cannot compare a low-torque-output small displacement 4-cylinder to this setup. We're talking about going from 3.5 liters to 3.2 liters here. I completely agree (as I previously mentioned), very little off-boost torque makes for a severely wanting setup, which a low-compression 1.8 liter or 2.0 liter will have. My wife's old '02 Malibu with a 3100 automatic had enough N/A torque to satisfy me (hp was a different story). I don't think I'll be left wanting with this one.
I built my dream twin-turbo L98 Camaro that made an estimated 700 lb/ft at the flywheel at 15psi. I know torque, off boost and on boost. I don't think I'll be left wanting with this one.

I've helped build and driven plenty of other turbo cars (and my turbo motorcycle) with highly varying setups. I'm not new to turbo'ing either.

The 'essence' of turbocharging can be left up to interpretation. In the most technical terms, it's simply stuffing more air into a given static displacement via leftover exhaust energy. Any amount of turbine-driven pressure above atmospheric on any ICE engine fulfills that definition.
To me, the philosophical 'essence' of turbocharging is driving a high-boost turbocharged car and getting that ultra-surge of power with that jet-sounding intake rush with the sexy note of the turbine spooling through the tailpipes. The rush, the sound, the excitement!
If it puts out the power I want at the boost level I want to deal with, then there's no problem.

I want to push the Getrag as far as I possibly can before swapping, and while I don't want to flat-out abuse it, I want to be able to drive it like a racecar (which means flat-out abusing it, heh). I may not have anything to worry about as far as extra torque output (or extra shock-loading) from 3.5l vs. 3.2l, but again, there are more reasons than just that for me to do it this way. Read my above post (post #4). It isn't about eeking out every ounce of the highest hp possible, though again...

I probably won't have to turn up the boost any more (or significantly more) to get the same hp, it'll just be at a higher RPM.
To throw in another factory example, compare the latest thirdgen F-body TPI engines.
The best 305 (LB9) made 230hp and 300 lb/ft. The best 350 (L98 ) made 245hp and 345 lb/ft. The engines were identical other than the bore and the intake valve diameters. The 305 had 1.84" intakes and the 350 had 1.94" intakes (tipping slightly in the 350's favor). Otherwise they had the same TB, TPI intake, compression ratio, camshaft, exhaust from the head to the tailpipes, etc etc.

The 350 has 14.7% more displacement, 15% more torque, and only 6.5% more hp (with larger intake valves and less shrouding even).


All that being said, here's the beauty of using the 'throwaway' TGP shortblock first. It'll let me get a good idea of how the setup works with 3.1 liters (though with the longer stroke, smaller bore) without spending 'real' money on the bottom end, how much boost it'll take on 93, and just generally how it spools and feels to drive. All of the above (3200) is subject to change depending on these results, but in the past I've had a very good track record of guessing how a particular setup would turn out so I'm reasonably confident in my future combo, though I admit that I could always be way off. The important part is that it's getting there!

One way or another, I miss my TT IROC-Z to no end so this Fiero better be good, really good.

[ALLTRBO]

Oh, and since no one has answered my question in the other forum, can someone help me out here? Here's (roughly) what I posted...

I have a TGP 3.1 shortblock in my Fiero (with 3400/3100 heads/intake) and it has a custom accessory drive done for the swap.
I want to know if all that will bolt directly onto a 3500 block (timing cover/water pump and everything that bolts to that), or if it won't bolt up, what are the reasons? I'd like to know what mods I'll have to make to use it.

[Joseph Upson]

Oh, and since no one has answered my question in the other forum, can someone help me out here? Here's (roughly) what I posted...

I have a TGP 3.1 shortblock in my Fiero (with 3400/3100 heads/intake) and it has a custom accessory drive done for the swap.
I want to know if all that will bolt directly onto a 3500 block (timing cover/water pump and everything that bolts to that), or if it won't bolt up, what are the reasons? I'd like to know what mods I'll have to make to use it.

There may or may not be a difference in the size of some of the timing cover bolts which shouldn't be difficult to address, definately when installing the Fiero timing cover on a 3.1 block. I've done so many experiments I'm not sure anymore. I did the twin turbo IROC Z28 1986 back in 1995 from the ground up except for the exhaust going from the turbos. Never had more fun driving the Z than I did my slower turbo Fieros, performance cars should be small and agile, not four seaters. The Z was like riding in a very fast closet that was hard to keep pointed straight when the boost came on, Fieros squat and go.

[ALLTRBO]

Oh, I forgot the title from the other thread mentioning that it's the stock TGP timing cover (normal Gen II), not the Fiero. Sorry for the confusion.
Thanks for the reply.

I know exactly what you mean about the turbo thirdgen. I swapped in a T56, and in cooler weather the car would spin the 275's into its 4th gear.
I planned on going further with the chassis but decided that since I had to give up on either the Fiero or the Camaro, I'd stick with the lighter car with better handling and more traction. :/ It's a no-brainer for a sports car, but a turbo IROC-Z has been my dream car since I was 10 or so, so it was really hard to let it go.
So I had (still have) a no-torque all-traction powerful turbo car, and I had an all-torque no-traction powerful turbo car, and that's why I'm building something with what should be just the right balance (and with better handling).

[ALLTRBO]

It's coming along...

I hereby officially designate SFI as "Single Fire Injection" since I'm using the '730.









The bottom half of the trunk was cut off at the factory ledge and re-welded to make room for the post-turbo exhaust and a rear diffuser.

[RedZMonte]

I hereby officially designate SFI as "Single Fire Injection" since I'm using the '730.

Im not familiar with what '730 is.... I assume by "Single fire injection" it is running a batch fire setup where all cyl spray fuel at once? my biddies CRX race car we setup on Accell DFI on a Batch fire and made tons of power, worked well (430HP Turbo on a Single cam D16 1.6L).

S

[ALLTRBO]

Yep. '730 is the last three digits of the part number of a GM OBD1 ECU. That's the easy way to tell apart the multitude of them that GM made. The '730 is one of the most common, and it's a speed density and batch fire ECU. I forget all of the applications, but they include 90-92 F-bodies, Some (all?) Berettas and Corsicas, and many other late 80's to early 90's GM cars. Most of them have different code masks to run the various engines.

Batch fire is perfectly fine for most operating conditions because the fuel doesn't sit around for long enough to cause a problem, but when you get into large injectors and large cams on smaller engines, idle tends to be harder to keep smooth. That's where SFI (the real SFI, heh) shines in comparison.

Related; I'm going to run into issues trying to idle 65lb/hr per injector on my 3.2 liter when I get to it, but that'll be helped somewhat by modifying a Syclone/Typhoon ECU ('749) to accept an extra injector driver so I can run 6 peak/hold (low impedance) injectors. I'll probably also have to raise the idle a bit. It's just hard for the mechanical components to restrict that much fuel flow when it isn't needed.