Crossfire Upgrades: My Quest for More Air and More Fuel

[KANE]

I've been kicking this thread around for a while- just now getting to posting it.

So, this is a detailed, personal account of what I have done with my 1982 Corvette's Crossfire system as I have upgraded it.


First steps to performance

So a few years ago, my '82's cam was replaced with a Comp Cam. The original cam was a bit worn and there was a desire to upgrade it since it was coming out anyway. Here's the cam specs for both-

1982 Corvette Stock Cam Specs-
Lift: .410" / .423" @ 114 LSA

Comp Cam Compu-Cam Specs-
Lift: .425" / .440" @ 112 LSA

It has never been down a drag strip. Nor has the car been dyno'ed in it's completely stock form . So, I have no clue how that car performed stock before the cam swap in terms of numbers. I do know it runs better than most 82s I've driven- and I feel safe attributing that to the cam. The car has also been in my family for 24 years- so I know the car well.

However, we all know the Crossfire intake's ports are smaller where the intake meets the heads. While speculation runs rampant, it is what it is... and I decided to try an intake that might move more air. So, I purchased a second generation Renegade intake from Dynamic Crossfire Solutions. I had no issues with the company, purchase, or install- everything went accordingly.
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Renegade Intake

Having had the chance to look over the intake, I'm impressed and it seems so far worth every penny.
​

• Eddie Motorsport in CA did the casting. It was packaged well with a lot of brown crumpled shipping paper to protect the top plat and manifold during shipping.​
• It came with detailed instructions, gaskets, and hardware. Honestly, if I didn't know the intake, I'd say that it could have been from Holley, Jegs, or another aftermarket company.​
• Having looked over a stock CFI and this intake, I'd say "wow- GM was clearly tied to a tree with EPA/emissions/mileage requirements."​
  • There is no passage under the intake for coolant on the DCS piece- instead, coolant travels through the crossovers at the front and back like a normal intake. Really, a lot of thought has gone into this thing!​
  • The inside plenum looks as if the runners are the same length as a TPI's base plate- but a bit larger and square in nature. The top plenum plate is the same height as the OEM piece- but dimensionally it is a little larger in circumference on the sides along the heads. This I think is the place where DCS has made the magic: they have effectively solved the problems related to the runner port sizes at the head, the EGR system, and the coolant tunnel.​
  • Still fits the large head HEI, but it is bigger in nature.​
  • All threads are tapped and all surfaces that mate to other parts are machined smooth- just as you'd expect. There is no slop in terms of thin spots or excessive casting flash. Also- the previous versions cast by the old foundry were off just a little- so, the plenum was actually a millimeter to the right or left (depending on your vantage point). It looks like Eddie Motorsport got it right.​

Getting it running with the intake

I will say the machining job was great- however, when they say "here's the bolt tightening sequence"... they are serious. I've never had to get an intake down one bolt at a time... following the sequence to the letter. Usually I've been able to get all the bolts finger tight- and then torqued down according to the sequence. Not here- you need to actually start and tighten each bolt according to the sequence. There was very, very little slop in the machining, casting, etc. Very impressive for what it is.

Anyway, the car ran well at first. It seemed to have really been woke up when it was cold. And... then as it warmed up... it ran rough. :crazy


The short story: 31 year old parts were slowly failing. Not failing completely, but enough that with all of them failing together it was a mess. The computer was going out, the O2 sensor was on its way out, and the fuel pump wasn't pushing quite enough fuel. And, when it was cold- it ran okay.:ugh

My friend balanced the throttlebodies- thankfully, they weren't off by much- and made sure there wasn't anything I might have missed in the intake swap.

Oddly enough when the CFI ECM starts to go out, it doesn't always stop completely. Instead, it will intermittently lose portions of its functionality and won't throw codes. I had open loop- but not closed loop. In fact, it will almost appear like the computer is running fine- you'd need a lot of datalogging to see the inconsistencies in operation as the result of the ECM's complete loss of closed loop capability. In other words, the CFI ECM wasn't able to throw codes to let me know it was on its way out.

The O2 sensor was close to where it should be, but again after 31 years... it too was on its way out. Not a total loss- but a degraded loss all the same.

The fuel pump was the most interesting. It was pushing a few pounds less than it should have. Again, not a total failure- just another worn out part. No- I don't have a fuel pressure gauge to set between the throttle bodies, so this one was something that I wouldn't have found on my own.

Still, it was running a bit rough when warmed up.
​

Fuel / Air / Spark

I've upped one- the air aspect- and need to make sure the other two are accounted for. Fuel will come in two ways- a performance oriented chip and then re-adjusted pressure. Spark will come in the form of base timing and the chip. I have plenty of the middle one.

As my friend and I talked, I decided to look at adding just a bit more fuel. Not much- but a little bit. So, I decided to install slightly larger injectors (TBI Caprice police package cars push slightly more pounds of fuel) or a hypertech chip (slight revision to the fuel maps). It's close enough to stock with the cam and intake that I could wring a bit more out of it with a couple of incremental, small adjustments.
​

The Fuel aspect...

So, I clearly needed to get more fuel since I was moving more air with the Renegade and the cam. Here's what I did:
​

• Moved up to 68lb GM injectors that cross reference to the 1992 Caprice with the 9C1 police package. Tom at DCS has been emailing and talking with me about what other things I need to wring as much out of it as possible. Tom said that I was going to need more injector with the cam as the stock cam & intake are at the upper limits of the stock injectors. He was right.​
• Replaced the diaphragms on the pressure regulator (rear unit) and the one on the front unit. Thought after 31 years it wouldn't hurt- those do stretch out and lose their ability to keep the right pressure after a good number of years.​
• Removed the anti-tamper plug on the bottom of the regulator bowl and bumped it up just a bit. I'll dial it in when the center pressure line comes in. This line has a fitted gauge from DCS- I plan to keep it on just long enough to set the pressure- and then I'll swap back to the OE line. I'm looking forward to setting it at 14-15lbs.
  
  With just the injectors-NO MORE LEAN CONDITION AT IDLE OR IN CLOSED LOOP!!!!!
  
  That's right- it stopped throwing codes!!!
  
  I did take it out and test run it. I'm impressed- it is starting to run really, really well. Once I get the fuel pressure dialed in and the fuel maps worked out- it'll be set. The intake, cam and injectors have started to wake it up!
  
  I get the feeling the hp and torque curves have shifted. Now it runs all the way to 5k rpm like a freight train. The specs on the cam say it's good from 1k-5k rpm and I'd say it drives like it too. And, that would make sense since being lean was a sign of moving more air as the result of the cam and intake.
  
  Here's what I think: I've known that car for 23 years- so, I know it very well. When I took out for a run on the passing gear (35-70mph) it took off like a shot. I've never felt it run like that- it climbed through the rpms and the mph and it was scary fast for itself. Is it LT1 fast? Not sure- I think my '95 with the MN6 and 3.42 would be slight faster in acceleration (not sure if I'll ever find out either). But I do know that for itself- for being an '82 with CFI- that it runs much, much better and seems to behave (power band) more like my Trans Am's LT1 than what it was as a CFI car. Especially between 35-70mph.
  
  Moreover, it sounds different- in a subtle way. In neutral, it idles between 700 and 800rpm. In gear it is a perfect 600 rpm.
  ​

What's next...

Within the next week, I should have the fuel pressure set, the chip, and the base timing set. I'll update this thread with what happens.


​

 

[xfirez51]

What have you done about re calibrating the tune?

 

[KANE]

What have you done about re calibrating the tune?

I'm going to start with a JET Stage II chip. The cam should work with an OEM ECM- and the intake would work with an OEM ECM. Will they all play together nicely with only bigger injectors? We'll see. What I do know is the injectors helped in a big way. I still need to set the fuel pressure though.

If that doesn't work, I'm going to look at the '7747 ECM swap and then go down the road with a custom chip.


This is very much a test and learn project.

 

[xfirez51]

I'm going to start with a JET Stage II chip. The cam should work with an OEM ECM- and the intake would work with an OEM ECM. Will they all play together nicely with only bigger injectors? We'll see. What I do know is the injectors helped in a big way. I still need to set the fuel pressure though.

If that doesn't work, I'm going to look at the '7747 ECM swap and then go down the road with a custom chip.


This is very much a test and learn project.

Don't waste your money IMO. Your "test and learn" project has been done many times. You could learn from others that have already done this. Will this work with the stock ECM? Maybe, but not very well and not optimally. As for ECMs, skip the 7747 and go to EBL at DynamicEFI.
Also suggest you visit ThirdGen.org

 

[KANE]

Don't waste your money IMO. Your "test and learn" project has been done many times. You could learn from others that have already done this. Will this work with the stock ECM? Maybe, but not very well and not optimally. As for ECMs, skip the 7747 and go to EBL at DynamicEFI.
Also suggest you visit ThirdGen.org

Isn't "Don't waste your money IMO" an ironic statement when owning a Vette?



Having done several EFI retrofits that I personally pieced together from the ground up- TBI and Multi-Port- I'm fairly familiar with GM fuel injection. They all had some degree of custom tuning, which required testing the tunes and adjusting them accordingly. Hence, test and learn.

JMHO- The big unknown is the true performance capability of the intake. It's fairly new to the market and there aren't as many people who have experience with them as there are folks who have experience with other styles, designs, and types of intakes.

Not sure if I want to go down the EBL route at this time. There are pro's and con's to everything.

Thanks for your thoughts on the 7747 vs. EBL. Have you used an EBL before?

 

[xfirez51]

Isn't "Don't waste your money IMO" an ironic statement when owning a Vette?



Having done several EFI retrofits that I personally pieced together from the ground up- TBI and Multi-Port- I'm fairly familiar with GM fuel injection. They all had some degree of custom tuning, which required testing the tunes and adjusting them accordingly. Hence, test and learn.

JMHO- The big unknown is the true performance capability of the intake. It's fairly new to the market and there aren't as many people who have experience with them as there are folks who have experience with other styles, designs, and types of intakes.

Not sure if I want to go down the EBL route at this time. There are pro's and con's to everything.

Thanks for your thoughts on the 7747 vs. EBL. Have you used an EBL before?

I tuned both on my 84Xfire using a ported stock manifold and larger cam. The 7747 doesn't have the resolution, speed, flexibility or functionality EBL has. Not to mention flash capability. Not even close.

 

[KANE]

I tuned both on my 84Xfire using a ported stock manifold and larger cam. The 7747 doesn't have the resolution, speed, flexibility or functionality EBL has. Not to mention flash capability.

So, what did you run with in terms of a cam? OE heads?

Also- what did your tune look like- how much did you add/alter in terms of fuel/spark/etc?

 

[xfirez51]

Ran a custom Comp Cams grind. Full roller setup w Comp roller lifters, Crane SS 1.6 full roller rockers and hardened pushrods. Heads were TFS 23d 190cc runners and 64cc chambers giving 10.25:1 compression. Cam spec was 218@ .050", 269@.006, .528" lift w 1.6, 108LSA, 53d overlap. Stock bottom end.
Added tons of fuel. Fuel and spark curves totally different, no comparison. Had twin 80# BB injectors, Aeromotive VAFPR 10.5psi at idle/20psi@WOT. Can't do that with a 7747. Also, the TBIs parallel plumbed for fuel. Ported Xfire manifold w 2.13" dia. TBs.
285rwhp/347rwtq. 13.3 best 1/4mile on street tires, 104.5mph best trap speed.
So BTDT. I had my 84 for 24 yrs also. BTW, ZF-6 trans-plant and Dana 44 3.45s.

 

[KANE]

Ran a custom Comp Cams grind. Full roller setup w Comp roller lifters, Crane SS 1.6 full roller rockers and hardened pushrods. Heads were TFS 23d 190cc runners and 64cc chambers giving 10.25:1 compression. Cam spec was 218@ .050", 269@.006, .528" lift w 1.6, 108LSA, 53d overlap. Stock bottom end...

Yeah- for that level of modification, you definitely needed the EBL. Sounded like it was a good mill.

Did you think that even with the porting the intake was still the biggest point of restriction?



Incidentally, I have seen '82 put down around 160 at the rear wheels. That seems about right for 20% driveline loss at the wheels starting from 200 at the flywheel. So, your numbers are really good!

 

[Evolution1980]

...Heads were TFS 23d 190cc runners and 64cc chambers giving 10.25:1 compression.

I don't know how those heads compare to the stock heads, but given the cost of a good seat of heads, I don't think people typically(?) would do that if it wasn't a known significant performance bump. More often than not, it seems that changing heads can make the biggest difference of all the items you listed. On that part alone, I think the performance parameters changes/requirements may have eclipsed the full potential of the 7747, or at least started bumping up against its limits.
I'll be curious to see if Kane finds himself bumping up against it's 30 year old walls or not. I'm also curious what GeekInAVette and C4C5Specialist think, as they are both solid knowledge references as well.

 

[xfirez51]

I don't know how those heads compare to the stock heads, but given the cost of a good seat of heads, I don't think people typically(?) would do that if it wasn't a known significant performance bump. More often than not, it seems that changing heads can make the biggest difference of all the items you listed. On that part alone, I think the performance parameters changes/requirements may have eclipsed the full potential of the 7747, or at least started bumping up against its limits.
I'll be curious to see if Kane finds himself bumping up against it's 30 year old walls or not. I'm also curious what GeekInAVette and C4C5Specialist think, as they are both solid knowledge references as well.

I chose the TFS heads and they were fairly new at the time. Pretty comparable to AFR heads and a bargain for $600. What people forget is that the Xfire is a small block w a TBI induction. It responds to all the same mods any other SBC does. The 7747 is an upgrade from the stock ECM. It's also thoroughly hacked but was built for truck motors. Higher performance really requires greater resolution and a faster processor. The ALDL Datastream is too slow at 1frame/sec. EBL is 17.

 

[82ColEd]

Thanks Kane for posting the thread up here.
I've followed a plenty of them when the old xfire site was still up and am familiar with DCS. Friend had the Renegade and was pushing the car to a new height at 250+ km/h on the Autobahn before he left the foot off. He did however mod the brakes, springs etc to be able to cope with the biest he created. If you want, i'll dig out the info he had posted a while back on the german site and post it here. Or invite him to the thread. He has sold the car since and gone C5 on us, but the car is still around.

Now i know i can pester you about reading the WinALDL for me.. :L


Keep us posted as you go, very cool stuff !!

-Stefan

 

[KANE]

Quick update...


Set the fuel pressure between the TBs. Remember, I already have 68lb injectors- so, I didn't need to go crazy with the psi.

As a point of reference, it was set from the factory at around 9 psi. :ugh I bumped it to 10 psi before I got started tuning today. Now, it did run okay up and through 3/4 throttle when set at 10 psi- but WOT wasn't exactly what I had been looking for. That's why in my passing gear comments in the previous posts I was getting closer- but it was not where I wanted to be.


Here goes:

• 14 psi- I set it here first. During open loop- seemed okay, triggered SES in closed loop :eyerole. My thoughts: it didn't respond as quick on throttle blips. Also, it seemed to set off the SES once as soon as it entered into closed loop.
• 15 psi- Tried going the other way now to see what higher pressure would do. Well, it was too high :ugh; and it set off SES light rather quickly. Seemed to be sluggish before setting off the SES. My thoughts: this was not going to work for the chip, intake, injectors, and cam combo. By setting the SES off while merely warming back up, it was obviously not viable.
• 13 psi- multiple tests and no SES ; multiple downshifts and rolling start take-off tests to make sure there were no surprises. My thoughts: it seemed to like this setting the best of all the tests.

During road tests, it seemed to accelerate more like an LT1 motor car. Now as it pulls really, really hard to and over 5k rpm with no feeling of power loss in the range above 4k- 4.5k rpm.


Tested out a couple of chips too. Seemed to like Hypertech's calibration the best . The JET chip seemed to want to run in SES mode ad.

 

[KANE]

Whadda ya' know... a defective fuel injector.

More adjustments... and a discovery.


Found out this morning where some of my tuning challenges may have been coming from: the passenger side injector. That makes part number two that may not have been right from the supplier, BWD. ad

I really hadn't noticed this before- but the spray pattern seemed a little...well, best described as being "different". ;squint:



Yeah- that's because it was leaking :ugh. If ever only so slightly- but still leaking a little bit. What tipped me off was that I could see a droplet form and then drop ever so often... and the spray didn't seem as crisp as the driver's side injector. No, I did not need a scan tool to figure it out... I could see it and it was time to head back to the parts store for a warranty covered replacement. Especially after I shut it down and it began to really dump fuel. :eyerole



Now I know why I had struggles with tuning- especially in the upper rpms, and why 13 psi seemed like it was working the best. The problem wasn't bad enough to trigger the SES (i.e.- too rich)- but enough to do some weird things in terms of behavior. I must have been inadvertently trying to compensate for an out of spec injector.:duh




Why am I sharing? Because this is real- defective parts happen. From time to time we all get parts that don't work like they should- and those defective parts create havoc in terms of diagnosis, performance, and tuning. We usually expect a new part to work- it's our instinct to trust that it will work. And when it doesn't...:W




***SIGH***


New injector installed... now, both injectors are doing what they should.



Back to 14 psi and some road tests... stay tuned.

 

[xfirez51]

I think I may still have injectors from my Xfire days. Also, I don't recall but the 84 has only one O2 sensor. It may not be on the passenger side so rich/lean won't show up. Bumping FP by 1psi will affect all areas of fueling including AE. SOTP really doesn't tell you anything and increasing FP isn't going to change the cam/cylinder head dynamics

 

[KANE]

Also, I don't recall but the 84 has only one O2 sensor. It may not be on the passenger side so rich/lean won't show up. Bumping FP by 1psi will affect all areas of fueling including AE. SOTP really doesn't tell you anything and increasing FP isn't going to change the cam/cylinder head dynamics

Yep- only one O2 sensor on the 82 & 84s.


So... clearly, it wouldn't run correctly with a leaky injector. Where I had the pressure set before was essentially compensating for the fact an injector was leaking, unbeknownst to me. Lower- but not that low... and leaky- but not that leaky. Yes, I was impacting all areas of fueling to include AE with the pressure as I was attempting to get it all to work together. Which was difficult because I had something out of sync (the injector).

Also- I don't think I have a cam that is so big that I'm going to run into problems with the factory tune. The dynamics just aren't that great yet between the cam and the heads.

 

[KANE]

...and some road tests... stay tuned.

To be clear, the Renegade intake has all of the same bolt locations as the original, however, the bolts (diameter) used to anchor down the throttle linkage, cruise control, and TV brackets are smaller than OE. This means there is some amount of movement left, right, front, and back that can occur until they are tightened down.

So... everything fits- and fits where it is supposed to- but you'll still need to make sure accelerator pedal travel (& cruise functionality) and TV line pressure & adjustments are where they should be.

For me, the goal of road testing was to make sure under load- and in real driving conditions that things worked like they should. And... they do. Finally!

 

[KANE]

As soon as the link goes live on VetteTube, you should be able to see and hear how it runs.




VetteTube - Corvette Videos, Corvette Babes, Corvette Pics, Corvette Burnouts, Corvette Mods

 

[Evolution1980]

As soon as the link goes live on VetteTube, you should be able to see and hear how it runs.

Link is working.

 

[82ColEd]

Good Job on the vid(s) Kane. I liked the high res one better.. (and yes, it sounds great)..

Any chance you can get one while driving? While i was watching your video, i was thinking: C'mon, put her into D and go..


-Stefan