Project MIDTRBO

[ALLTRBO]

It occurred to me recently that some of you may enjoy seeing my build, and I might get some good information from posting this here too.

The build thread is on Pennock's Fiero Forum, but I'll give a (semi) brief description here as well.

http://www.fiero.nl/forum/Forum3/HTML/000120.html

It's an '88 Fiero GT 5-speed with a TGP shortblock and a late Gen III top end being pushed by a Borg/Warner S258 with a .82 A/R T3 exhaust housing machined to fit, all controlled by a '730 ECU. I'm guessing it'll make somewhere around 350whp on ~12 psi, maybe a bit more.

Later on, after I get the tune and setup dialed in pretty well, I'm going to build up a stout "3200" destroker shortblock using a 3500 block and a 2.8 crank with Diamond pistons (.100 over 3400 pistons) and 5.85" forged SBC rods, and I'll probably have the top end ported and a decent matching cam installed. Along with the huge W/A IC setup that I'm building for it and serious fuel delivery and (Clutchnet) clutch upgrades, the setup should support about 600whp on high boost and race gas, with a smooth enough torque delivery that the Getrag 282 might handle it (if not, I'll upgrade to the F23 I believe it is?).

The suspension is also being worked over. It's already all rebuilt, and I'm working out the proper way to lower it without screwing up the geometry, which is an easy thing to do with the '88s (screw up the geometry, that is). There are ways... The wheel bearings will also be seriously upgraded, as will the wheel/tire combo.

I'm doing some body mods also, and will have a custom high-quality paint job.

I recently had to sell my twin-turbo IROC-Z to get a reliable daily driver, my 2010 Camaro V6 (3.6 DOHC VVT DI, 312hp) and I'm selling my 11-second AWD Talon and my stock AWD Talon, so the Fiero is going to be my only real sportscar to play with.
Because of that, I'm aiming for near ZR1 performance levels... Well, other than top-speed, reliability, ride quality and refinement. I'll save about $80,000 so that's okay with me.

Let me know what you think. If there's any questions I'll try to answer them, but most of it is covered in the build thread.

[SappySE107]

I am not sure why you want to destroke the motor, but I cannot think of any advantage other than less power...if that's an advantage.

[Superdave]

x2, that's a quick way to lose power. Cool project though.

[ALLTRBO]

*Less torque: With equivalent components (top end/cam/etc) a smaller displacement will usually make almost as much power but at a higher rpm. The torque, however, has a higher percentage difference. Look at the stock (late) 3100 vs. 3400 hp and torque for examples. The 3400 has 10 more hp (185 vs 175) but 15-20 more lb/ft. Though the 3400 has 6.9% more displacement (3350cc/3135cc), it has only 5.7% more hp, but 7.7% more torque.
They are, of course, identical other than the bore and slightly bigger TB on the 3400. So to make an even comparison put the 3400 TB on the 3100 and it might gain ~5 hp, bringing the hp advantage of the 3400 to only ~2.8%, but not really changing the peak torque. I've seen several examples of this, stock and modified, some to a more extreme degree...
I want less off boost torque to go easier on the tranny between shifts. It isn't much of a difference, but every bit adds up. Shock loading is what kills trannies, not really horsepower. However, I still want the reasonable off-boost torque of a V6 over a blatty l4 so I wouldn't go that route (been there done that with my Talon... no thanks).

*Rod/Stroke ratio: The 3100/3400 is 1.72:1, the 3500 is 1.79:1, and the "3200" will be 1.96:1
A higher rod/stroke ratio allows more resistance to detonation, which will allow me to run a bit more boost on the same octane (possibly making up for that slight hp drop without retaining that off-boost torque). In addition, the maximum piston speeds are slower.

*Less rotating mass: There will be less shock loading on the tranny between shifts, again. It isn't a lot of a difference, but every bit adds up. It will also use up less hp to turn the crankshaft, mainly at high rpm. Not only because the crankshaft is lighter, but also because the rod journals and the lighter counterweights take away weight from the outside diameter of the rotation, where it counts most.

*Rod availability: Using the 76mm crank and the 3400 pistons (.100 over) will allow me to use 5.85" SBC rods (slightly machined of course) for the perfect piston height vs. quench clearance vs. head gasket thickness, and very stout 5.85" SBC rods are somewhat easy to find, hence easier and cheaper than custom options that will handle ~650 hp.

*Crank strength: This one probably doesn't differ as compared to the forged 3500 crank, but comparing to the 3400 steel crank, there is more overlap between rod journals with the 2.8 crank. Many say that it doesn't matter because no one has ever broken a 3400 crank, but I don't think anyone has ever pushed ~650hp through one either (correct me if I'm wrong).

*RPM capability: All of the above adds up to a rotating assembly that'll probably beg for 7500 rpm with a few valvetrain mods and mild turbo cam upgrade, and intake and head porting (I'm talking about you, Ben. ). Maybe even 8000rpm. My heart skips a few beats at the thought of a jet-like spooling and screaming 7500-8000 rpm 60V6. The 282 doesn't care to shift above 7k from what I hear, but I think that's covered by an aluminum flywheel and lighter rotating assembly, along with my friend Will (aka: "The Dark Side of Will" on RFT and "Will" on PFF) with his awesomz 282 rebuild skillz, heh.

I could also add some panzy-arse reason like the extra gas mileage it could theoretically get, but this car isn't being built for economy, though it'll still be good enough.

I think that about covers it.

[86FieroSEv6]

Awesome build, man.


Now where's that damned Jealous button . . . ?

[ALLTRBO]

Thanks. Don't be jealous, it's still ugly and it doesn't even run yet! (Getting close though)

Here are a couple pics that some may appreciate. They're in the PFF thread, but if you don't want to read it you can at least try to figure out what happened here... (look harder. )





And here are couple pics of the goodies...





(The turbo is just resting on the flange)

[timg]

That's a great looking project and a nice choice of turbo. I'm looking forward to seeing how it performs. Thanks for the post! Please keep us updated.

Tim

[RedZMonte]

looked threw the PFF site, Loads more cool pics of the build. Looks good, excited to see the final results. there are a few guys with modified TGP setups making some great power. Cool project.

S

[ALLTRBO]

Thanks guys. I'll definitely keep up with the PFF thread, and I'll chime in here from time to time to summarize the progress.

[Dave96z34]

You de stroke an engine so you can run more boost safe.

[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?

[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.