New intake for crossfire = more HP!!!!

[toobroketoretire]

So will the easter bunny drop off some renegades for us?

I have a feeling it'll be June before we see them.

 

[nelson84]

Pouring them one at a time, I guess they are using one mold that is the best mold out of the three I have seen them using. Sounds like they will only pour about 2 a week??? Where was I on that list again. I hope I am next to get minehnoes. This old crossfire is just not fast enough for me anymore. It is running almost as slow as a ported crossfire. We need the real thing a"RENEGADE".

 

[Hib Halverson]

Wait a minute! I agree with Hib a lot - not as much as Hib agrees with Hib, but a lot.

Yeah, Catbert agrees with me a lot, but I agree with him that I agree with me even more, especially after I've had several bottles of "Old Arrogant Bastard Ale".

And speaking of things which are bastardized, that reminds me....

The facts about from where the 2xTBI induction came and the rumor that GM going to kill the 350 drove the CFI development.

Set the Wayback Machine for mid/late-70s.

GM was busy deciding what the new Corvette (originally planned for 1982 then slipped to 1983 and finally going to production as an 84 model in the Winter of 82-84) was going to be. There was never any intention to drop the 350 as the Corvette base engine.

The rumor that: GM was going to kill the 350 and go to a 305 and that's why the 2xTBI intake manifold has such small parts is either just plain bull or it's rumor stemming from confusion about the origins of the design of Tuned Port Injection which appeared in MY85 on both F- and Y-car.

The TPI intake manifold was sized for a 305 because GM believed that Camaro and Firebird Tuned Port 305s would outsell the L98 Corvette engine by a significant margin and GM didn't want to spend the money to tool-up two intake manifolds. So the L98 and LB9 hardware was the same.

Another reason the "kill-the-350-for-the-305" thing might have gotten started was the rare, 1980 LG4 California 305. All MY80 Vettes sold in CA had a 180-hp five-liter engine which was one of the first production cars with electronic engine controls. The reason why the CA cars for MY80 had a 305 is not because the 350 was doomed, but because the LG4 was destined as the base engine for other GM vehicles. Examples are the Monte Carlo, the Caprice, light trucks and other platforms. GM was already working on the LG4 prior to its decision to use it in Corvette as an answer to the last-minute, exhaust emissions regulations, more stringent than those in the other 49-states, which CA implemented for all MY80 cars sold in CA. Confronted with either not selling Vettes in CA that year or trying out the already-under-development LG4, GM made the smart choice.

Now, the final issue...why are the L83's intake ports so darn small?

In the mid/late-70s, with the new Corvette's powertrain under development, the state-of-art at the time was throttle body injection, however, Delco-Rochester did not have a throttle body assembly which flowed enough air to use on a Corvette engine. So someone thought, "Why not use two of them?"

Rather than use two on an in-line intake manifold and create a hood clearance problem, deep inside Chevrolet Engineering, some genius remembered that back in the late 1960s, the Camaro's '67-'69 302cuin had a factory dual-four-barrel, low cross-ram that Chevy homologated for the SCCA Trans-Am series. They took that idea and figured since it worked great on a race track, the same type of intake manifold would work great on a Corvette street use if fitted with two Rochester throttle body injectors.

Bad idea.:nono

As the system proceeded from design to development, Chevrolet soon found that while the system made pretty good high rpm power, it had terrible throttle response and awful low-speed driveability...so bad that not only was the engine off-idle and low-speed response very poor but it's exhaust emissions were lousy too.

What these wizards had forgotten is that the long runners, the huge plenum volume and the throttle body injectors so far from the intake valves, had fuel condensing out of the air stream and puddling on the runner floors when the velocity of the charge air dropped as the throttles were opened quickly.

What GM should have done was either stick with the QuadraJet 4ME for another two years or use a time machine to bring TPI from the future. But, most likely, for political, marketing and perhaps cost reasons, Chevrolet continued to try and put lipstick on a pig.

The development of CFI was long and difficult. I interviewed a GM Engineer back in the late 80s who told me he knew personally two powertrain engineers who paid for new homes with the overtime it took to get the CrossFire Injection to run well in the 82 Vette with an automatic trans and tall gearing.

The biggest problem was low port velocity at tip in. The eventual solution was to drastically decrease the port volume so that, when the driver whacked the throttle open at low rpm, port velocities remained high enough such that the air/fuel mix remained a vapor and little or no fuel condensed out of the air flow onto the port floors.

Of course, the end result of the tiny, high-velocity ports was significant restriction and poor performance at high rpm.

Yes...you'll gain power, maybe even a lot of power, if you increase the port and plenum volumes of a 2xTBI low cross ram intake manifold but the downside of doing that is degraded throttle response, poor low speed performance and, perhaps, increased exhaust emissions. Add to that the bigger camshaft that most hot rodders install and those problems get worse.

I don't think it's possible to mitigate those problems by simply increasing displacement because, then, you need to make the ports even larger.

Going to a modern hydraulic roller cam with more lift and less duration may help. Also going to a more modern, aftermarket ECM which may have a faster processor and more sophisticated controls might also help.

But in the end, when you put lipstick on a pig, you still have a pig.

CFI system modified with bigger ports and more plenum volume bolted onto an engine with a big cam, will make more power but the torque range will be more narrow and peaky with idle, off-idle and low speed somewhat degraded and perhaps significantly degraded.

Nelson 84 may love his Renegade, but from a practical standpoint, the way to get big power and torque out of 82 and 84 Vettes is to convert to port fuel injection or go back to a carburetor.

 

[toobroketoretire]

Options

As I have to keep the original intake manifold on my California '82, I'm stuck. I can either waste my time porting my Crossfire or use a Renegade. I won't mind the loss of some low end torque because I don't spend much time running my engine at real low speeds. I have always wanted power above 4000 rpm, and I know the Renegade will give me that power. I'm sure someone will be doing some dyno testing when these Renegades get released and I'm looking foreword to seeing the before and after results.

 

[TedC]

Shame on GM regarding performance limitations of the L83/CFI design and TPIs used on 350s. No wonder why the TPI has so much low end torque but runs out of steam at 4500 rpm. I've driven several L83s, and despite their bad reputation, I actually liked how they drove around town. It looks like both the TPI and to a greater degree the CFI design was not optimized for a 350. I do remember having fun in my 1985 Mustang GT 5.0 5 speed beating every single L83 I could find. Again, shame on GM. I would also extend my comments to the LT1 where GM installed such poor stock gear on such a better reving engine. I test drove three LT1s with 2.59 gears and could not accept the fact that GM ever produced these because of CAFE. A good performance street car like a vette should be better optimized from the factory. I've been keeping my eye on the soon to be released 2011 Mustang GT. Yes, I'm a American car fan regardless if it comes from Ford, Chevy, or Mopar. I would like to test drive the new 412HP 5.0 with six speed. For me, that is optimized performance in a $30K package. I look forward to seeing the results of this new intake. Save the L83 and the wave.

 

[toobroketoretire]

Shame on GM regarding performance limitations of the L83/CFI design and TPIs used on 350s. No wonder why the TPI has so much low end torque but runs out of steam at 4500 rpm. I've driven several L83s, and despite their bad reputation, I actually liked how they drove around town. It looks like both the TPI and to a greater degree the CFI design was not optimized for a 350. I do remember having fun in my 1985 Mustang GT 5.0 5 speed beating every single L83 I could find. Again, shame on GM. I would also extend my comments to the LT1 where GM installed such poor stock gear on such a better reving engine. I test drove three LT1s with 2.59 gears and could not accept the fact that GM ever produced these because of CAFE. A good performance street car like a vette should be better optimized from the factory. I've been keeping my eye on the soon to be released 2011 Mustang GT. Yes, I'm a American car fan regardless if it comes from Ford, Chevy, or Mopar. I would like to test drive the new 412HP 5.0 with six speed. For me, that is optimized performance in a $30K package. I look forward to seeing the results of this new intake. Save the L83 and the wave.

You hit the nail right on the head when you used the word "optimized". The Crossfire Injection system worked very well on the 305" engine but NOT on the larger 350" engine. To do it right, G.M. should have made a larger version of the Crossfire Injection system for the 350" engines. But instead of using a larger version, they stuck the same identical system on both engines and the 350" engine got screwed. The CFI just wouldn't flow enough air to allow the larger 350" engine to wind beyond 4000 rpm without running out of air. I have driven my L83 for 22 years now and it's pitiful to see the tachometer race upwards only to see the engine abruptly fall flat on it's face at 4000 rpm. The Renegade will solve the 350" engine's breathing problem by supplying enough air to allow 6000 rpm or more if the 350" has enough camshaft duration.

 

[Hib Halverson]

There might be another problem with different intake manifolds for the L83 and that is calibration.

Where do people believe they are going to find aftermarket calibrations for the ECMs in 82s and 84s?

 

[toobroketoretire]

There might be another problem with different intake manifolds for the L83 and that is calibration.

Where do people believe they are going to find aftermarket calibrations for the ECMs in 82s and 84s?

Hib, I was under the impression the MAP sensor and the ECM would take care of the calibration. Am I mistaken? DCS claims they simply bolted on their high flowing prototype and gained 33 more horsepower and 16 ft/lbs of torque. They didn't recalibrate anything to gain that additional power so why do I need to recalibrate anything? About 18 years ago I gutted a Crossfire and cut the entire bottom out. I welded on a 1/4" thick aluminum plate on the bottom and I had NO runners at all. The only "runners" were the head's ports. In other words, all I had was a giant plenum feeding the head's ports. The manifold produced terrific top end power and I retained the same fuel mileage as I originally had. But I couldn't pass the stringent California emission tests with that gutted manifold, so I put my port matched Crossfire back on. As I ran that gutted Crossfire without having to recalibrate anything, it seems like I'll have no trouble running a Renegade that simply has larger runners.

 

[nelson84]

I was reading some posts on this renegade on another forum, and it looks like alot of people are excited about it. Even an article in super chevy is going to happen.

 

[Hib Halverson]

Hib, I was under the impression the MAP sensor and the ECM would take care of the calibration. Am I mistaken? DCS claims they simply bolted on their high flowing prototype and gained 33 more horsepower and 16 ft/lbs of torque. They didn't recalibrate anything to gain that additional power so why do I need to recalibrate anything? About 18 years ago I gutted a Crossfire and cut the entire bottom out. I welded on a 1/4" thick aluminum plate on the bottom and I had NO runners at all. The only "runners" were the head's ports. In other words, all I had was a giant plenum feeding the head's ports. The manifold produced terrific top end power and I retained the same fuel mileage as I originally had. But I couldn't pass the stringent California emission tests with that gutted manifold, so I put my port matched Crossfire back on. As I ran that gutted Crossfire without having to recalibrate anything, it seems like I'll have no trouble running a Renegade that simply has larger runners.

With due respect, I'd like to suggest that you all research how GM engine controls work before you decide that..."the MAP sensor and the ECM would take care of the calibration."

There are many sources of information on the subject. CarTech books, in particular, has some good titles.

 

[KANE]

With due respect, I'd like to suggest that you all research how GM engine controls work before you decide that..."the MAP sensor and the ECM would take care of the calibration.".

Hib's all over it!

Toobroke, the L83 is designed to run withing a range of conditions- optimized to the OEM set up.

When you change things out- your ECM can't always keep up. That new intake will put you out of the range that GM programmed that ECM to deal with. You'll need a custom tune to get the most out of it.

Take it from a guy who has done GM EFI swaps.

 

[toobroketoretire]

Hib's all over it!

Toobroke, the L83 is designed to run withing a range of conditions- optimized to the OEM set up.

When you change things out- your ECM can't always keep up. That new intake will put you out of the range that GM programmed that ECM to deal with. You'll need a custom tune to get the most out of it.

Take it from a guy who has done GM EFI swaps.

But my engine is no longer a stock L83. It got an Erson 214/214 .480" lift roller cam and Dart heads back in 1996, then I added a set of 1.6 roller rockers last year. Now I just need a freer breathing intake manifold to go along with my previous modifications.

 

[nelson84]

But my engine is no longer a stock L83. It got an Erson 214/214 .480" lift roller cam and Dart heads back in 1996, then I added a set of 1.6 roller rockers last year. Now I just need a freer breathing intake manifold to go along with my previous modifications.

Which roller rockers did you get? Are you using the stock valve covers? I am ordering a set this summer, I just don't want to order the wrong ones, I want them to fit under the stock valve covers.

 

[vetteboy86]

You'll need a custom tune to get the most out of it.

Take it from a guy who has done GM EFI swaps.

Have you done tunes yourself? I have been tuning my 383 for almost three years now. Seems like there is always something else to modify. With my lack of time, my learning curve is slower than normal.

But my engine is no longer a stock L83. It got an Erson 214/214 .480" lift roller cam and Dart heads back in 1996, then I added a set of 1.6 roller rockers last year. Now I just need a freer breathing intake manifold to go along with my previous modifications.

Does DCS offer any tuning capabilities for the Crossfire platform?

 

[toobroketoretire]

Which roller rockers did you get? Are you using the stock valve covers? I am ordering a set this summer, I just don't want to order the wrong ones, I want them to fit under the stock valve covers.

I got a set of Competition Cams investment cast steel 1.6 ratio roller tip rockers so they would fit under the stock magnesium valve covers. I think they cost me about $130. With the 1.6's, my gross valve lift is now .513"; .033" higher than the old 1.5's produced. I have wound my engine up to 6500 rpm in 1st gear with no evidence of any valve float, but I intend to set my up-shift points to about 5500 rpm. Something more suited to my engine's torque curve. Now I just need my new Renegade to finish my engine modifications off.

 

[KANE]

I have been tuning my 383 for almost three years now. Seems like there is always something else to modify. With my lack of time, my learning curve is slower than normal.

I was lucky- it only took six months to get the tune where I wanted it. I had a lot of help from a very experience tuner. Your mods are far more elaborate than my set up was.

The TPI and an L82 cam plus 1.6 rockers was fairly easy to get moving. What did take me a while to figure out that I needed to get it set to 14 degrees of initial timing so that my ECM could pass its self test- at 6 degrees, I wasn't getting any knock when the ECM would advance the timing to its max, where it was supposed to induce knock.

A certain participant in this thread may remember those emails I sent to him as he and I hashed out what I needed to do. Thanks again buddy !

 

[toobroketoretire]

I was lucky- it only took six months to get the tune where I wanted it. I had a lot of help from a very experience tuner. Your mods are far more elaborate than my set up was.

The TPI and an L82 cam plus 1.6 rockers was fairly easy to get moving. What did take me a while to figure out that I needed to get it set to 14 degrees of initial timing so that my ECM could pass its self test- at 6 degrees, I wasn't getting any knock when the ECM would advance the timing to its max, where it was supposed to induce knock.

A certain participant in this thread may remember those emails I sent to him as he and I hashed out what I needed to do. Thanks again buddy !

Kane, are you saying you ran a 14 degree initial advance? I have set mine as high as 10 degrees but never up to 14 degrees. Do you suggest I try 14 degrees to see if I can induce a ping under wide open throttle? And how much advance will the ECM produce over the initial advance? I am also running an ADS Super Chip, but the chip won't allow me to pass my bi-annual smog test. Every 2 years I have to put the stock chip back in so my car will pass smog. Then once I pass smog, I put the ADS back in. And do you have any other suggestions? I'm all ears...............

 

[KANE]

Kane, are you saying you ran a 14 degree initial advance? I have set mine as high as 10 degrees but never up to 14 degrees. Do you suggest I try 14 degrees to see if I can induce a ping under wide open throttle? And how much advance will the ECM produce over the initial advance? I am also running an ADS Super Chip, but the chip won't allow me to pass my bi-annual smog test. Every 2 years I have to put the stock chip back in so my car will pass smog. Then once I pass smog, I put the ADS back in. And do you have any other suggestions? I'm all ears...............

I'm suggesting that you learn as much as possible about GM EFI first!

Your set up is totally different.

My engine had 8.5 : 1 compression and needed a lot of advance to run correctly.

GM 90-92 MAP based TPI systems can advance the timing as far as 20 degrees forward. My engine's max advance is 34 degrees. Since that is the range of the advance, I needed to get the computer to hit that number- knowing that it can only advance 20 degrees from whatever base timing is set to.

This is the "in the weeds" type of understanding needed to develop the maximum amount of power on a modified engine.

 

[toobroketoretire]

I'm suggesting that you learn as much as possible about GM EFI first!

Your set up is totally different.

My engine had 8.5 : 1 compression and needed a lot of advance to run correctly.

GM 90-92 MAP based TPI systems can advance the timing as far as 20 degrees forward. My engine's max advance is 34 degrees. Since that is the range of the advance, I needed to get the computer to hit that number- knowing that it can only advance 20 degrees from whatever base timing is set to.

This is the "in the weeds" type of understanding needed to develop the maximum amount of power on a modified engine.

Are you saying the ECM is capable of advancing the timing 20 degrees? Knowing a sbc likes a total of 36-38 degrees of timing, then an initial advance of 16 degrees would give me 36 degrees of timing. Right?

 

[vetteboy86]

Depending on load the ECM can advance the timing up around 45-47 degrees. As a matter of fact stock TPI tables have several cells in this range.

Install a wideband 02 and you might learn something about how the motor responds to the new intake.