I could refute some of your points one by one, but I'm convinced that would be pointless. If you all want to believe that the only reason TPI makes more HP an torque than a TBI is the size of the ports go ahead.
84 cross fire
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
If fuel routing, or origin of introduction to the air flow is a "problem", how do you explain the excellent functioning and undeniable effectiveness of a carburetor for over 100 years?
I've been restraining myself from saying this, but I can't any more: I feel bad for the people who paid you to work on their Corvettes. CLEARLY, I did far better w/my own CFI car(a Trans Am), by myself, then you would have. And I'm money ahead for not having paid for your "services".
Last edited by Tom400CFI; Nov 24, 2007 at 02:43 PM.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
But no, "most of us" DON'T know what Paul meant. When a "Corvette mechanic" of 20 + years tell us that:
Originally Posted by Paul Ruggeri
CFI sprays the fuel on the throttle plates, like a carb. TPI sprays the fuel into the intake ports at a higher pressure. This is why ultimately TPI can produce more HP
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
...well, that's just wrong. Where "fuel is sprayed" is NOT what causes the discrepancy in power between the two systems; the CFM and crossection of the stock runners is. Maybe Paul needs to articulate himself better? What might help is if he uses science and proven theory, and not annecdotal comparisons, like L98's vs. LT1's.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Tom400CFI
Why is comrehension/comunication SO difficult? Even when it is clearly written??
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Dominic Sorresso
BTW, where the fuel is sprayed on a TBI system is NOT the throttle plates. A properly functioning TB injector has a cone like spray meant to distribute the fuel onto the wall of the venturi just above the throttle plate. The air rushing past the fuel "shears" it off the wall and that's how it ends up in suspension. Just another Xfire/TBI factoid for those not familiar with how it works.
Except there is no venturi in an EFI TB. It (they) has (have) straight throttle bores.
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Former Vendor
Joined: Nov 2006
Posts: 2,482
Likes: 3
From: Carmichael ca
Maybe I was unclear with my original point. It is; that the difference in hp between an 84 and an 85 is not just,"NOT JUST", the restrictive ports on the 84. That the fact that they use two different FI systems has "something" to do with it. When I said that TBI sprays the fuel on the throttle plate, I should have said above the throttle plate. That may have reduced some of the venom hurled my way.
Basically by spraying the fuel under higher pressure, producing better atomization, directly into the ports, you get a more controlable and precise mixture. I believe this is part, not all, of the reason for the hp difference.
If you disagree, OK. I still think what I've just said is true, but obviously I'm not changing any minds. Perhaps my arguements aren't effective or my sarcasm has put some people off. Most people take it with a sense of humor, some can't.
Here's a thought I had. Suppose, and I'm not saying this is even possible, but just as a sort of mental experiment. You took an 85 and removed the throttle body. In its place you put a TBI. Running the engine off the TBI instead of the the port injectors, would it still make 230 hp?
Trying hard to play nice, Paul
Basically by spraying the fuel under higher pressure, producing better atomization, directly into the ports, you get a more controlable and precise mixture. I believe this is part, not all, of the reason for the hp difference.
If you disagree, OK. I still think what I've just said is true, but obviously I'm not changing any minds. Perhaps my arguements aren't effective or my sarcasm has put some people off. Most people take it with a sense of humor, some can't.
Here's a thought I had. Suppose, and I'm not saying this is even possible, but just as a sort of mental experiment. You took an 85 and removed the throttle body. In its place you put a TBI. Running the engine off the TBI instead of the the port injectors, would it still make 230 hp?
Trying hard to play nice, Paul
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
Maybe I was unclear with my original point. It is; that the difference in hp between an 84 and an 85 is not just,"NOT JUST", the restrictive ports on the 84. That the fact that they use two different FI systems has "something" to do with it. When I said that TBI sprays the fuel on the throttle plate, I should have said above the throttle plate. That may have reduced some of the venom hurled my way.
Basically by spraying the fuel under higher pressure, producing better atomization, directly into the ports, you get a more controlable and precise mixture. I believe this is part, not all, of the reason for the hp difference.
...Trying hard to play nice, Paul
Basically by spraying the fuel under higher pressure, producing better atomization, directly into the ports, you get a more controlable and precise mixture. I believe this is part, not all, of the reason for the hp difference.
...Trying hard to play nice, Paul
Thank you for trying. But, I think there are at least 3 of us in this thread and many more other Xfire users that have proven porting of the manifold runners explains the difference in horsepower with no other changes. However, this in no way negates your point regarding the conceptually superior capability of a PFI v TBI systems. We all agree with you. But I'll bet I could put a carb on a ported Xfire manifold and make the same if not more hp than the same short block with an 85 TPI setup on it.
If you've ever heard of the Xram, its claim to fame was restoring the 25hp differential by subbing a Weind manifold base with an adapter to mount the TBI units. Port a Xfire manifold and you get the same results.
I just don't think it gets any simpler than that.
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Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
BUT in the case of this conversation, I don't think that there is any real world, measurable benefit from the port injection, as it came in '85 w/a slow ECM and batch-fire. To wit a real word comparison was made by me when I had my CFI TA (and it was close to stock), vs. an '85 TA that was a 305 TPI. Both cars were F-bodies, both "loaded" (assume similar weight), both sporting 305 long blocks, one with CFI and one with TPI. My CFI car would beat the TPI car at the drag strip, and get better fuel milage on the highway. (1 mph consistently, hand calculated, me driving both cars). The TPI car had a 3.07 rear, and my CFI car had a 3.23 rear. Both cars passed MA emissions test easily and about equally well.
Inspite of those real world results, I'm not going to say that since MY CFI car ran better at the strip, and got as good gas milage or better than the TPI car, that CFI is better -becuase I know that in principle, it's not. I'm saying that the differences realized by a port/batch-fire system vs. a TBI system will NEVER be noticed or measurable in the real world, and that's why I answered YES, above. No reason why you can't get fuel to an engine from before the throttle plates, effectively.
In addition to my "novel" above, what Dom and CFI-EFI have said; porting the CFI and adding fuel to match, results in TPI matching or beating performance. Proof that the delta in performance is cause by air flow challenges w/the tiny CFI runners, as cast.
Last edited by Tom400CFI; Nov 25, 2007 at 09:49 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Paul Ruggeri
Maybe I was unclear with my original point. It is; that the difference in hp between an 84 and an 85 is not just,"NOT JUST", the restrictive ports on the 84. That the fact that they use two different FI systems has "something" to do with it.
Originally Posted by Paul Ruggeri
If you disagree, OK. I still think what I've just said is true, but obviously I'm not changing any minds. Perhaps my arguements aren't effective or my sarcasm has put some people off. Most people take it with a sense of humor, some can't.
Originally Posted by Paul Ruggeri
Here's a thought I had. Suppose, and I'm not saying this is even possible, but just as a sort of mental experiment. You took an 85 and removed the throttle body. In its place you put a TBI. Running the engine off the TBI instead of the the port injectors, would it still make 230 hp?
RACE ON!!!
Instructor
Joined: Feb 2007
Posts: 217
Likes: 0
From: ELK-MAHA Nebraska
I have a question on porting the CFI Manifold....I found this link on it and .... In the pictures, they have removed the EGR and Blocked it off completely.....What are the Benefits of removing the EGR tunnel ( Sorry! I'm new the manifold porting game )
Can someone tell me what can be achieved after removing the EGR tunnel... anyone have an answer...? thanks ! i have plans to Do this soon and since you have to tear it down to port match it i was curious to know it it improved the performance w/o the EGR
Thanks
.....And sorry if i Hijacked the thread http://www.technovelocity.com/chevyh...-fire manifold
Can someone tell me what can be achieved after removing the EGR tunnel... anyone have an answer...? thanks ! i have plans to Do this soon and since you have to tear it down to port match it i was curious to know it it improved the performance w/o the EGR
Thanks
.....And sorry if i Hijacked the thread http://www.technovelocity.com/chevyh...-fire manifold
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
I have a question on porting the CFI Manifold....I found this link on it and .... In the pictures, they have removed the EGR and Blocked it off completely.....What are the Benefits of removing the EGR tunnel ( Sorry! I'm new the manifold porting game )
Can someone tell me what can be achieved after removing the EGR tunnel... anyone have an answer...? thanks ! i have plans to Do this soon and since you have to tear it down to port match it i was curious to know it it improved the performance w/o the EGR
Thanks
.....And sorry if i Hijacked the thread http://www.technovelocity.com/chevyh...-fire manifold
Can someone tell me what can be achieved after removing the EGR tunnel... anyone have an answer...? thanks ! i have plans to Do this soon and since you have to tear it down to port match it i was curious to know it it improved the performance w/o the EGR
Thanks
.....And sorry if i Hijacked the thread http://www.technovelocity.com/chevyh...-fire manifold
Intermediate
Joined: May 2008
Posts: 29
Likes: 0
From: Lively ON
Wow, Harsh words for one of the most reliable C4s.
I am not sure if you want to run sub 10s.........
If you want to look out for things on your car. You need to focus your eyes on the 'other' components. And by that you'll need to start looking at the rear wheel bearings, half shafts, and U-joints. All together there are 4 U-joints, replace them all if you can't find where the PO already did.
The Master cylinder will go, wait for a Hot day and you may experience blow by. The MC is a 1 hour job if you don't count the time pulling the plastic cups off your old MC and getting them onto the new MC. It is an easy Job.
The rear wheel bearings are probably out of spec by now. Search for a thread on the subject by JrRifleCoach. If you have a shutter that you can't pinpoint it most likely is a wheel bearing or.......
The suspension durometors have all deteriorated. All the bushings need to be replaced, there is a kit for ~$90 that has everything you need. Just understand that it leads to a lot of labor. For instance, GM sells a the rear Dogbones for ~$45 each and it takes minutes to pull one off and replace as it is held on by two nuts......but the bushings are fractions of the cost. You have to press the old ones out and replace. The real is not near as hard as the front setup.
Do you have an Auto or 4+3 tranny? That is a whole different post.
Your Dash will start blinking....that is a grounding issue. Could be the solder has gotten old and cracked on the PCB or the connectors have corroded. Worse case is the dash is really dim and the Turn signals and bright light (blue) indicator are real bright.
Your Headlights will stop flipping up or down. Don't fret this one. There are plastic gears inside that strip out over 22 years. putting new gears in there will take about an hour each side. Basically pulling out the motor and cracking it open to expose the gears is all it takes. pull out the old ones and put in the new ones........put it all back together, Done.
Make sure you check your Spark Plug wire looms (the plastic doodads that hold your wires in place). If they are old and brittle it won't be long until your wires fall and contact each other or exhaust components creating a "CrossFire" that is not by design. Buy new Looms and the really thick Plug wires and replace all that right now.
The Valve covers are leaking about 1/8 of a quart of oil for every tank of gas. If you have an oil leak check there first.
The radiator is being choked for airflow by all the trash that is in between it and the condenser. Your engine will run a little hot due to this. There is a shroud covering both and is held in place by the coolant hoses. When you flush and change the hoses, make sure you pull the shroud off and clean out in between them. Do this before any drastic changes to address the heat issues.......like a lower Temp Thermostat.
I'm sure I'll think of other things but that is enough to spend the first year of ownership of an '84.
I am not sure if you want to run sub 10s.........
If you want to look out for things on your car. You need to focus your eyes on the 'other' components. And by that you'll need to start looking at the rear wheel bearings, half shafts, and U-joints. All together there are 4 U-joints, replace them all if you can't find where the PO already did.
The Master cylinder will go, wait for a Hot day and you may experience blow by. The MC is a 1 hour job if you don't count the time pulling the plastic cups off your old MC and getting them onto the new MC. It is an easy Job.
The rear wheel bearings are probably out of spec by now. Search for a thread on the subject by JrRifleCoach. If you have a shutter that you can't pinpoint it most likely is a wheel bearing or.......
The suspension durometors have all deteriorated. All the bushings need to be replaced, there is a kit for ~$90 that has everything you need. Just understand that it leads to a lot of labor. For instance, GM sells a the rear Dogbones for ~$45 each and it takes minutes to pull one off and replace as it is held on by two nuts......but the bushings are fractions of the cost. You have to press the old ones out and replace. The real is not near as hard as the front setup.
Do you have an Auto or 4+3 tranny? That is a whole different post.
Your Dash will start blinking....that is a grounding issue. Could be the solder has gotten old and cracked on the PCB or the connectors have corroded. Worse case is the dash is really dim and the Turn signals and bright light (blue) indicator are real bright.
Your Headlights will stop flipping up or down. Don't fret this one. There are plastic gears inside that strip out over 22 years. putting new gears in there will take about an hour each side. Basically pulling out the motor and cracking it open to expose the gears is all it takes. pull out the old ones and put in the new ones........put it all back together, Done.
Make sure you check your Spark Plug wire looms (the plastic doodads that hold your wires in place). If they are old and brittle it won't be long until your wires fall and contact each other or exhaust components creating a "CrossFire" that is not by design. Buy new Looms and the really thick Plug wires and replace all that right now.
The Valve covers are leaking about 1/8 of a quart of oil for every tank of gas. If you have an oil leak check there first.
The radiator is being choked for airflow by all the trash that is in between it and the condenser. Your engine will run a little hot due to this. There is a shroud covering both and is held in place by the coolant hoses. When you flush and change the hoses, make sure you pull the shroud off and clean out in between them. Do this before any drastic changes to address the heat issues.......like a lower Temp Thermostat.
I'm sure I'll think of other things but that is enough to spend the first year of ownership of an '84.
Ok, you don't understand how freaked out I am. I bought mine last year and I, almost, word for work, did that last summer...
Add the power steering rack blowing up inside and trashing the pump, you've got yourself a fully years work.
Pro
Joined: Feb 2005
Posts: 560
Likes: 0
From: Hamilton New Jersey
These posts always get to me.. I especially hate when people say sell the car and buy a different car.. it's especially laughable when they tell you to upgrade to a tpi car.. Here are the facts, your cfi car is a CORVETTE. IT has a chevy small block in it, one of the most common and supported engines in the aftermarket pars business. Sure there might not be a whole lot of support for the crossfire itself but so what? Its just an induction system.. port the heck out of the base, do what you can with it, upgrade to an x-ram, if it doesn't suit your needs upgrade to something else (NOT tpi), don't sell your whole car just because of the induction system on it. Sorry for the rant these posts get to me.. I hate people bashing on these cars and I really hate the suggestion to sell your car and buy a different car, what it comes down to is it's a small block chevy and there are so many different things you can do and change to taylor fit it to your needs. Keep your car, upgrade it in a way that makes you happy. In the end you'll love it more than something that you simply bought.
Pro
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From: KINGS PARK NY
Just my $.02
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
You didn't define "real mods" but based on your extremely brief and unhelpful (to the OP) post, I'd say that you must not have tried hard enough, b/c "enough fuel" isn't that hard to come by, in my experience.
Le Mans Master
Joined: Dec 2004
Posts: 5,488
Likes: 1,352
I got a great idea !!! Swap over to a L98 set up and then once that's done you can swap over to a LTX manifold 
The guys rambling about how much better the L98 is are delusional. Yes it's superior however all the assache involved to swap over to a different intake that hits a wall @ 4500 rpm is funny. If it were mine I would mod the Crossfire set up. I do not see the purpose in spending alot of money to "upgrade"
The guys rambling about how much better the L98 is are delusional. Yes it's superior however all the assache involved to swap over to a different intake that hits a wall @ 4500 rpm is funny. If it were mine I would mod the Crossfire set up. I do not see the purpose in spending alot of money to "upgrade"
Last edited by JD'S WHITE 93; Jun 2, 2008 at 08:45 PM.
Pro
Joined: Apr 2008
Posts: 694
Likes: 1
From: Spokane WA
BTW, where the fuel is sprayed on a TBI system is NOT the throttle plates. A properly functioning TB injector has a cone like spray meant to distribute the fuel onto the wall of the venturi just above the throttle plate. The air rushing past the fuel "shears" it off the wall and that's how it ends up in suspension. Just another Xfire/TBI factoid for those not familiar with how it works.
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
Mine ran a 13.37 and trapped at 104.5mph with those "plugged" injectors. If yours are spraying on the plates at idle, I'd look for new injectors.