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| Returning Fiero Owner - Let's Talk 2.8 Breathing (Page 1/14) |
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SpaceLion
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MAR 28, 02:08 PM
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Hello everyone! It's been a long time. I'm back on the forum because I just picked up an 86 1/2 fiero gt with a nice little laundry list of goodies done to the 2.8 including: bored over to 3.2, 3.1 crank neutral balanced with 7.25" flywheel, ARP rod bolts, a comp cam, 1.6 roller rockers, ported heads, 2.44 g/s injectors, a performance true dual exhaust and a chip to manage the calibration for the injectors.
Now, one of you I suspect, may find that this all sounds familiar. If that's the case I'd love to find the previous owner on here and talk. But that's not why I'm making this thread. Let's talk intake.
So for all of my research, it seems that our cars have trouble breathing around 4500, give or take. And the guy I'm buying this from specifically told me it drops off at 5k. Based on what I've seen, the restrictive intake plenum looks guilty, at least in part. And I wondered what people have done to help this engine breath.
I've seen the Trueleo intakes out there, which are out of production, and I have seen claims here on this forum that they don't age well and have never provided dyno results, at least with a same before and after (no addition modifications between dyno)
I've seen that Black Top Racing was working on a dual intake, which looked cool and probably expensive, but from what I can tell, they are out of business now.
I've heard of a member here using the intake from a 2.8 firebird with a 3D printed adapter for the throttle body. I'd be curious what the benefits are to this one, just read about it. No details on CFM increase.
I've also considered going small, reliable forced induction, mostly just to get it breathing right in the high RPMs. maybe 6-9 psi. But I'm not sure what compression it's running. I'm not even sure what the stock compression is, or if people have had bad experiences going forced induction on the ol 2.8.
At the end of the day, it looks like all of the online stores that I used to dream shop for performance parts just a few years ago are gone. V8 archie looks like it's still around. The Fiero store, though that all looks like support for stock parts. I'd really like to come up with a solution for this anemic intake, as I suspect with everything that has been done to the engine, if it could breath proper, it would probably wake up even more. Any suggestions? And am I missing any good online performance and styling product stores that are still around?
Thanks in advance, I'm glad to rejoin the ranks of fiero owners!
-Mike
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jjd2296
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MAR 29, 06:58 AM
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RayOtton
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MAR 29, 08:42 AM
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I have the ported exhaust, "Dawg Style" UIM, relieved y-pipe, hi-flow cat, Hypertech chip and a 57MM throttlebody. Basically all the breathing mods. Each one added a little to the performance but then I did the 1.6 rockers and WOW! what a difference.
I consider the rocker mod to be the one that brought all the pieces together, giving me a very nicely balanced car which also looks completely stock.
As for the RMP power limit, I can say unequivocally that the rockers made a huge difference. Where the stock car ran out of breath at about 4500RPM's, the modded car easily pulls all the way to 5500RPM's and there still some left but that's as far as I want to push a 30 year old engine even if it only has 60K miles on it. In fact, being an automatic I have to manually shift because the factory shift point is way too low for the modded engine.
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fieroguru
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MAR 29, 12:28 PM
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This thread has pictures of most of the intake manifold modifications.
http://www.fiero.nl/forum/Forum2/HTML/135882.html
This is a modification to the middle intake that helps as well.
[This message has been edited by fieroguru (edited 03-29-2020).]
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jjd2296
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MAR 29, 01:20 PM
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I’m planning on doing this as well
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SpaceLion
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MAR 29, 04:40 PM
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jjd2296 - You've gotta let me know how that turns out. Looks like you've put some real effort into that! Looks good.
RayOtton - Now that's what I'm talking about, I really just wanted to get her breathing right up to at least 5500 maybe with a little more if I'm even in a situation where I need to tap it. I plan to eventually autocross her, so for just getting to that corner without shifting up and then down it could be useful. The throttle body and Dawg Style UIM's, who made them? Are they still around? And what kind of modification did you need to made the throttle body electronics play nice?
Fieroguru - You're the man! Thanks for that resource!
Thank you everyone for the constructive on topic responses! That's what I'm talkin about![This message has been edited by SpaceLion (edited 03-29-2020).]
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RayOtton
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MAR 29, 09:22 PM
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| quote | Originally posted by SpaceLion:
The throttle body and Dawg Style UIM's, who made them? Are they still around? And what kind of modification did you need to made the throttle body electronics play nice?
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The throttle body was bored by a member on here, about 5 years ago so I don't recall the name. Try a search of the site, if nothing comes up drop me a line and I'll see if I have an invoice laying around.
I bought the "Dawg style" UIM from a member here who listed it in the mall section. I don't know if anyone is making new ones but they do pop up now and again the the mall.
I didn't do a thing to the electronics other than replace the standard chip with a Hypertech one. Lots of people say they don't do anything but advance the timing curve and add a bit more fuel but hey, isn't that exactly what you need with airflow improvements?[This message has been edited by RayOtton (edited 03-29-2020).]
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pmbrunelle
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MAR 29, 10:37 PM
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| quote | Originally posted by RayOtton:
Lots of people say they don't do anything but advance the timing curve and add a bit more fuel but hey, isn't that exactly what you need with airflow improvements?
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No, you need timing retard with airflow increases.
Think about how a car has a vacuum advance can on the distributor; with more vacuum (i.e. light loads, low airflow), the timing must be more advanced.
The denser the air/fuel charge is in the cylinder, the faster the flame propagates away from the spark plug; the air/fuel charge is consumed more quickly.
If the spark is too advanced, you're just building up too much pressure, too early, while the piston is still rising in the compression stroke. This robs torque from the engine.
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RayOtton
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MAR 30, 08:25 AM
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| quote | Originally posted by pmbrunelle:
No, you need timing retard with airflow increases.
Think about how a car has a vacuum advance can on the distributor; with more vacuum (i.e. light loads, low airflow), the timing must be more advanced.
The denser the air/fuel charge is in the cylinder, the faster the flame propagates away from the spark plug; the air/fuel charge is consumed more quickly.
If the spark is too advanced, you're just building up too much pressure, too early, while the piston is still rising in the compression stroke. This robs torque from the engine. |
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We've had this discussion before and at the time I explained I'm no engineer so I can't argue theory.
However, hopefully you recall I do have empirical DATA to back up my point.
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pmbrunelle
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MAR 30, 01:18 PM
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| quote | Originally posted by RayOtton:
I didn't do a thing to the electronics other than replace the standard chip with a Hypertech one. Lots of people say they don't do anything but advance the timing curve and add a bit more fuel but hey, isn't that exactly what you need with airflow improvements?
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You asked a question (question mark at the end of your sentence), so I shared my point of view...
| quote | Originally posted by RayOtton:
We've had this discussion before and at the time I explained I'm no engineer so I can't argue theory.
However, hopefully you recall I do have empirical DATA to back up my point.
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There's no need to talk about peoples' occupations... arguments should stand based on their own merit, not because of a person's credentials.
If data doesn't agree with theory, then either the data is wrong, the theory is wrong, or both are wrong. If there is an inconsistency, that means we have some learning to do.
All propositions shall not be accepted at face value (including my own; nobody's word should be taken as-is). Everything should be scrutinized and picked apart... what remains after the collective debate is hopefully the truth.
By this method of collective verification and scrutiny, we can create a repository of quality information in the PFF archives.[This message has been edited by pmbrunelle (edited 03-30-2020).]
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