1991 ZR-1 Performance Question
01-06-2016, 08:22 AM
#21
Le Mans Master
Member Since: Oct 2004
Location: South-central Missouri
Posts: 6,314
Received 500 Likes
on
395 Posts
It DOES matter 
For those that have only the little green light indicating Full Engine Power on the 91s it prolly does not matter much except for the additional Chip costs and work removing the secondary (Not as simple as suggested). For those that have the FULL ENGINE POWER light up on the screen on their 1990s.....It is exciting. And once you fix the Vacuum Leaks the Secondaries are prolly the most reliable item on the engine Finding A Vacuum Leak
It is a LOT EASIER to fix the Vacuum System than it is to remove the Secondaries and you only have to fix the Vacuum System once. Fixing the Vacuum System does NOT require removal of the Injector Housings (which proper removal of the Secondaries Does Require Removal of the Injector Housings).
Secondly (No Pun Intended), The Full Engine Power Switch should be reconditioned Power Key Rebuild TIPS
For those that have only the little green light indicating Full Engine Power on the 91s it prolly does not matter much except for the additional Chip costs and work removing the secondary (Not as simple as suggested). For those that have the FULL ENGINE POWER light up on the screen on their 1990s.....It is exciting. And once you fix the Vacuum Leaks the Secondaries are prolly the most reliable item on the engine Finding A Vacuum Leak
It is a LOT EASIER to fix the Vacuum System than it is to remove the Secondaries and you only have to fix the Vacuum System once. Fixing the Vacuum System does NOT require removal of the Injector Housings (which proper removal of the Secondaries Does Require Removal of the Injector Housings).
Secondly (No Pun Intended), The Full Engine Power Switch should be reconditioned Power Key Rebuild TIPS
(Juuust messin' wid ya, Cliff!
)- NO coking buildup on secondary intake valves
- INSTANT throttle response w/ NO hesitation between gears
- Never no steeenking code "61" or any other SPT issues
- etc...
- etc...
- etc...
What's not to like???
01-06-2016, 08:31 AM
#22
Tech Contributor
Meh.... Now you're sounding like Scottfab! (Juuust messin' wid ya, Cliff!)
What's not to like???
(Juuust messin' wid ya, Cliff!)- NO coking buildup on secondary intake valves
- INSTANT throttle response w/ NO hesitation between gears
- Never no steeenking code "61" or any other SPT issues
- etc...
- etc...
- etc...
What's not to like???
I never get a code 61 or any code for that matter.
You get codes???
Less gas mileage is not to like and on a 1990 loosing the ability to switch on that FULL ENGINER POWER LIGHT is not COOL
And........some guys wire, strap, tie the secondaries open which is kind of Mickey Mouse in trying to eliminate the secondaries the EASY way
Last edited by Dynomite; 01-07-2016 at 12:14 AM.
01-15-2016, 09:36 AM
#23
Le Mans Master
Paul.....that is NOT nice to compare me to your friend
I never get a code 61 or any code for that matter.
You get codes???
Less gas mileage is not to like and on a 1990 loosing the ability to switch on that FULL ENGINER POWER LIGHT is not COOL
And........some guys wire, strap, tie the secondaries open which is kind of Mickey Mouse in trying to eliminate the secondaries the EASY way
I never get a code 61 or any code for that matter.
You get codes???
Less gas mileage is not to like and on a 1990 loosing the ability to switch on that FULL ENGINER POWER LIGHT is not COOL
And........some guys wire, strap, tie the secondaries open which is kind of Mickey Mouse in trying to eliminate the secondaries the EASY way
I originally strapped the secondaries open. Next step was to remove the throttle blades. Both worked fine for me until I finally removed the entire setup w the cam upgrade. Even now I will average 23-25mpg. On flats at a a cruise, my fuel economy gauge will read in the early 30's if I keep it below 75.
01-21-2016, 10:56 PM
#24
Pro Mechanic
Pro Mechanic
My two cents....
You had better have made a hell of a deal on a 91 which has a) obvious problems with the IP and 2) isn't making much power beyond the mid range.
Yes, the problem(s) could be as simple as a loose connection to the IP and a vacuum leak in the secondary port throttle system.
But, also, you could be looking at some significant repair bills as well.
There are a lot of ZR-1s for sale...why not find a car with less problems up front or...make the seller fix the problems, then buy the car.
You had better have made a hell of a deal on a 91 which has a) obvious problems with the IP and 2) isn't making much power beyond the mid range.
Yes, the problem(s) could be as simple as a loose connection to the IP and a vacuum leak in the secondary port throttle system.
But, also, you could be looking at some significant repair bills as well.
There are a lot of ZR-1s for sale...why not find a car with less problems up front or...make the seller fix the problems, then buy the car.
01-22-2016, 11:28 PM
#25
Instructor
Member Since: Nov 2008
Location: Houston TX
Posts: 102
Likes: 0
Received 0 Likes
on
0 Posts
My two cents....
You had better have made a hell of a deal on a 91 which has a) obvious problems with the IP and 2) isn't making much power beyond the mid range.
Yes, the problem(s) could be as simple as a loose connection to the IP and a vacuum leak in the secondary port throttle system.
But, also, you could be looking at some significant repair bills as well.
There are a lot of ZR-1s for sale...why not find a car with less problems up front or...make the seller fix the problems, then buy the car.
You had better have made a hell of a deal on a 91 which has a) obvious problems with the IP and 2) isn't making much power beyond the mid range.
Yes, the problem(s) could be as simple as a loose connection to the IP and a vacuum leak in the secondary port throttle system.
But, also, you could be looking at some significant repair bills as well.
There are a lot of ZR-1s for sale...why not find a car with less problems up front or...make the seller fix the problems, then buy the car.
01-25-2016, 01:25 PM
#26
Pro
Thread Starter
My two cents....
You had better have made a hell of a deal on a 91 which has a) obvious problems with the IP and 2) isn't making much power beyond the mid range.
Yes, the problem(s) could be as simple as a loose connection to the IP and a vacuum leak in the secondary port throttle system.
But, also, you could be looking at some significant repair bills as well.
There are a lot of ZR-1s for sale...why not find a car with less problems up front or...make the seller fix the problems, then buy the car.
You had better have made a hell of a deal on a 91 which has a) obvious problems with the IP and 2) isn't making much power beyond the mid range.
Yes, the problem(s) could be as simple as a loose connection to the IP and a vacuum leak in the secondary port throttle system.
But, also, you could be looking at some significant repair bills as well.
There are a lot of ZR-1s for sale...why not find a car with less problems up front or...make the seller fix the problems, then buy the car.
01-29-2016, 07:18 AM
#27
Team Owner
When i got my Lt-5 years ago, the secondary's were off line for years.
I used this information to get it all working again,
First time the newly repaired secondary's came on line car went sideways.
http://www.corvetteactioncenter.com/...diagnosis.html
Once that plenum is off its not all that complicated to work on.
I used this information to get it all working again,
First time the newly repaired secondary's came on line car went sideways.
http://www.corvetteactioncenter.com/...diagnosis.html
Once that plenum is off its not all that complicated to work on.
01-29-2016, 07:30 AM
#28
Team Owner
Fuel economy is noticeably compromised with secondary port throttle removal.
With the secondary valves closed, the entire intake charge comes into the combustion chamber via one intake valve - which creates a swirl effect and allows a lean mixture with effective power. Thus, a ***** to the wall 415 cid LT5 can get 26 mpg at 80 mph with 3:73s, while stock LT5s in this thread are bragging about a paltry 23 mpg at 70 mph and stock rear end - because the secondaries had been removed.
Loss of 30% fuel economy? No power gains? I'll keep the secondaries - thanks!
With the secondary valves closed, the entire intake charge comes into the combustion chamber via one intake valve - which creates a swirl effect and allows a lean mixture with effective power. Thus, a ***** to the wall 415 cid LT5 can get 26 mpg at 80 mph with 3:73s, while stock LT5s in this thread are bragging about a paltry 23 mpg at 70 mph and stock rear end - because the secondaries had been removed.
Loss of 30% fuel economy? No power gains? I'll keep the secondaries - thanks!
01-29-2016, 11:45 AM
#29
Le Mans Master
fuel mileage for me didn't change much at all, but one consideration is emissions. My HC went up significantly without the secondaries.
it's also not a "big power mod" even on the stokers. I got 5 HP (which is within dyno error range) and probably most of this improvement came from slight cleanup porting of the injector housings. marc said that the flow gains are very slight with about 3-6 cfm or so. The real improvement comes from opening up the secondary porting to make the mod worthwhile. I did see 8 ft lbs of torq increase in the mid range, but overall the juice isn't worth the squeeze with the possible exception of simplifying the car and keeping the secondary injectors flowing more so they stay clean and the things dynomite noted above.
I have to agree with Doc, it's really not a mod that is worth much for power, but parts left out don't break either and Mr. Haibeck can hook you up if you want to run the right chip and eliminate them.
it's also not a "big power mod" even on the stokers. I got 5 HP (which is within dyno error range) and probably most of this improvement came from slight cleanup porting of the injector housings. marc said that the flow gains are very slight with about 3-6 cfm or so. The real improvement comes from opening up the secondary porting to make the mod worthwhile. I did see 8 ft lbs of torq increase in the mid range, but overall the juice isn't worth the squeeze with the possible exception of simplifying the car and keeping the secondary injectors flowing more so they stay clean and the things dynomite noted above.
I have to agree with Doc, it's really not a mod that is worth much for power, but parts left out don't break either and Mr. Haibeck can hook you up if you want to run the right chip and eliminate them.