Different 3.4l piston/head compatibility (Page 3/7)
82-T/A [At Work] AUG 11, 10:38 AM

quote
Originally posted by 1985 Fiero GT:


Hmm, now I don't know, this is honestly the first time actually looking into turbos seriously, there's a lot to learn, I have no idea on target power, but from what I'm reading, 15lbs of boost roughly doubles na power? If a 3.4pr makes 160 stock, my porting and everything I've done to the 2.8 and can transfer to a 3400 has added estimated 20hp (based on other people's dyno results with the same mods and my 0-60 time), making a 3.4 closer to 180, remove 5% from compression drop, 170hp na, that would be about 340hp at 15psi boost? I'm sure with inefficiencies, real world data, etc, it would be less than that, but is my math mathing?

Whew, just got through reading all 11 pages of "The White Bug", lots of great information that's applicable for this, I'd probably end up with the 7.7:1 compression, and boosting it from there.




The "White Bug" thread is pretty awesome, and some amazing work on that car too... fantastic engineering.

Only thing I wanted to add is that as you build this motor, you may want to consider also swapping out the cam, if you can. It's not required, obviously; however, it can dramatically improve the efficiency of the engine and how it interacts (and pairs) with the turbo you're adding.

https://www.enginelabs.com/...ic-camshaft-designs/


Also, off the cuff, but if you're going to build a new motor... my recommendation is to get yourself another cradle, and build an inexpensive cradle dolly. You can then build the engine on the cradle while you still have your car complete and ready to go. It seems like most people don't really consider this, but it dramatically improves the efficiency of your time and efforts, and limits the down-time of your car being out of commission.

Imagine being able to calmly build your perfect engine swap on a cheap yet super sturdy engine cradle dolly, as you continue to enjoy driving your Fiero every day. Exhaust, turbos, suspension, you name it... all installed and ready to go on the cradle ... so you only have to spend an afternoon swapping it out (Note, may require two cradles dollies for obvious reasons).


Shameless plug of ferocious 92 screaming horsepower in all its glory...
1985 Fiero GT AUG 11, 10:43 AM

quote
Originally posted by 82-T/A [At Work]:
The "White Bug" thread is pretty awesome, and some amazing work on that car too... fantastic engineering.

Only thing I wanted to add is that as you build this motor, you may want to consider also swapping out the cam, if you can. It's not required, obviously; however, it can dramatically improve the efficiency of the engine and how it interacts (and pairs) with the turbo you're adding.

https://www.enginelabs.com/...ic-camshaft-designs/


Also, off the cuff, but if you're going to build a new motor... my recommendation is to get yourself another cradle, and build an inexpensive cradle dolly. You can then build the engine on the cradle while you still have your car complete and ready to go. It seems like most people don't really consider this, but it dramatically improves the efficiency of your time and efforts, and limits the down-time of your car being out of commission.

Imagine being able to calmly build your perfect engine swap on a cheap yet super sturdy engine cradle dolly, as you continue to enjoy driving your Fiero every day. Exhaust, turbos, suspension, you name it... all installed and ready to go on the cradle ... so you only have to spend an afternoon swapping it out (Note, may require two cradles dollies for obvious reasons).





I'll look into camshafts too, and I'll definitely try to get another cradle, there are a few parts Fieros near me, I'm sure I can get a cradle, hopefully in fairly good shape, that's a great idea though.
pmbrunelle AUG 11, 11:40 AM

quote
Originally posted by 1985 Fiero GT:
Hmm, now I don't know, this is honestly the first time actually looking into turbos seriously, there's a lot to learn, I have no idea on target power, but from what I'm reading, 15lbs of boost roughly doubles na power? If a 3.4pr makes 160 stock, my porting and everything I've done to the 2.8 and can transfer to a 3400 has added estimated 20hp (based on other people's dyno results with the same mods and my 0-60 time), making a 3.4 closer to 180, remove 5% from compression drop, 170hp na, that would be about 340hp at 15psi boost? I'm sure with inefficiencies, real world data, etc, it would be less than that, but is my math mathing?



Your math is mathing, but you are missing some factors, most notably the reduction in air density due to air temperature increase (as ericjon262 hinted at). Refer to the ideal gas law.

I do not agree with your assumption that a 3.4L engine is more powerful than a 2.8L engine; if they are both breathing through the same heads and intake, then I think the power potential is the same. That said, your math is correct; the science or judgement behind the math is less clear.

Even with ideal adiabatic compression, when air is compressed, it becomes hotter. In reality, with the churning and friction of a real turbocompressor, the temperature rise is even greater.

Yes, it is important to have some power goals/estimates, because you need this to size different items (fuel pump, injectors, clutch torque capacity, etc).

Eventually, once you hit the pressure/temperature/time limit (where knock occurs) for the fuel you are running, then the assumption that power is proportional to airflow breaks down.


quote
Originally posted by 82-T/A [At Work]:
Also, off the cuff, but if you're going to build a new motor... my recommendation is to get yourself another cradle, and build an inexpensive cradle dolly. You can then build the engine on the cradle while you still have your car complete and ready to go. It seems like most people don't really consider this, but it dramatically improves the efficiency of your time and efforts, and limits the down-time of your car being out of commission.

Imagine being able to calmly build your perfect engine swap on a cheap yet super sturdy engine cradle dolly, as you continue to enjoy driving your Fiero every day. Exhaust, turbos, suspension, you name it... all installed and ready to go on the cradle ... so you only have to spend an afternoon swapping it out (Note, may require two cradles dollies for obvious reasons).



Yes and no... what you say is definitely true for bolting together stock parts.

However, when making custom parts, then the cradle needs to go in and out of the car to verify fitment.
82-T/A [At Work] AUG 11, 12:45 PM

quote
Originally posted by pmbrunelle:
Yes and no... what you say is definitely true for bolting together stock parts.

However, when making custom parts, then the cradle needs to go in and out of the car to verify fitment.



That's a really good point that I totally glossed over. I still think the extra cradle can be a good idea, but I wonder if it would make sense to design say... a cardboard or fiberglass "box" that you could use for measurement purposes. Something that you could loosely build and measure in the engine compartment and then be able to place (at pre-defined points on a stock cradle) where it would go so you could ensure your complete engine system fits within those dimensions.

Height is always the one that I forget about too. Even the Iron Duke comes within an inch of the decklid... they had to notch out space for the air cleaner on the 84's grill.
pmbrunelle AUG 11, 01:19 PM

quote
Originally posted by 82-T/A [At Work]:
That's a really good point that I totally glossed over. I still think the extra cradle can be a good idea, but I wonder if it would make sense to design say... a cardboard or fiberglass "box" that you could use for measurement purposes. Something that you could loosely build and measure in the engine compartment and then be able to place (at pre-defined points on a stock cradle) where it would go so you could ensure your complete engine system fits within those dimensions.

Height is always the one that I forget about too. Even the Iron Duke comes within an inch of the decklid... they had to notch out space for the air cleaner on the 84's grill.



Fieroguru constructed a wire-frame to simulate the trunk wall.

He used it to help ensure fitment during the construction of his exhaust manifolding:
https://www.fiero.nl/forum/...000123-37.html#p1451
1985 Fiero GT AUG 11, 04:08 PM

quote
Originally posted by pmbrunelle:


I do not agree with your assumption that a 3.4L engine is more powerful than a 2.8L engine; if they are both breathing through the same heads and intake, then I think the power potential is the same.



My estimate was based on the Camaro 3.4, which makes 160hp through the Fiero heads and a similar intake and more restrictive exhaust, and I've added 20hp to the 2.8, all in transferable items that impact the 3.4 equally well. the 3400 make 180 stock, I'm definitely not expecting that na with Fiero heads and intake haha, but the 3400 block with lower compression will still outperform the 2.8, I don't know by how much, but a bit at least.
1985 Fiero GT AUG 11, 04:14 PM

quote
Originally posted by 82-T/A [At Work]:


That's a really good point that I totally glossed over. I still think the extra cradle can be a good idea, but I wonder if it would make sense to design say... a cardboard or fiberglass "box" that you could use for measurement purposes. Something that you could loosely build and measure in the engine compartment and then be able to place (at pre-defined points on a stock cradle) where it would go so you could ensure your complete engine system fits within those dimensions.




I may or may not get a second cradle, maybe not though, as I'll only have 1 trans, nowhere for me to get another, so I'll probably do engine first, then position the turbo with everything else in the car, I'll definitely make use of CAD (cardboard aided design), as I learned in The White Bug thread haha.
1985 Fiero GT AUG 11, 04:16 PM
Wow, talk about impulsive haha, I imagined this swap 2 nights ago, now I'm making arrangements to acquire a 3400 block. Wow, well maybe I will be doing this after all!
1985 Fiero GT AUG 11, 07:07 PM
Is there any issue with using the stock Fiero rubber intake snorkel under boost? I don't know how strong it would be, and where I'm imagining the turbo would allow it (3/4 of it) to be used between the turbo and the throttle body.

EDIT: realized my measurement was off, never mind!

Would I have to disconnect the PCV connector there, I assume I don't want my crankcase pressurised at 15psi!

[This message has been edited by 1985 Fiero GT (edited 08-11-2024).]

82-T/A [At Work] AUG 11, 07:09 PM

quote
Originally posted by 1985 Fiero GT:

Wow, talk about impulsive haha




Yep... I can be the same way. This is why I got into the watch hobby... it's budget neutral and they're more valuable over time. But man... I forgot how expensive cars are. When my daughter's done with her Fiero, it'll still maybe be a $5,000 car, totally restored. Hahah...