EGR Elimination
Former Vendor
Joined: Nov 2005
Posts: 11,792
Likes: 255
From: Ossining New York
St. Jude Donor '07-'08-'09-'10-'12-'13-'14
Sounds like fun!
HEY CHUCK!! Car's running great. That's why I'm taking it apart!
I know.....I know.....but hey, everyone needs something to do.
I picked up a complete Super Ram that I'm going to install. Of course, can't have the Super Ram without the matching cam. Then of course, the heads are the weak spot, then the exhaust......and so it goes on.....
One of two things are going to happen. Either I can't get it to run (which really isn't going to happen) and I'll have to have you correct it.
Or, once I get it to run, I'll bring it up to you for tuning.
Once I decide on heads, I think AFR is a little to proud of their heads. I'm looking at Brodix and Patriot at this point. I hear what you're saying about compression. I can get 62CC heads which will put the compression at 9.5:1, the factory is 10.25. I've done all the math and feel pretty comfortable with that number. 9.5 is where the older L98s run. I can't find heads smaller than 62CC.
As far as the torque converter, that's my next step, after the engine work. Then a shift kit. At which point I take a breather and see what I like or don't. I'll go from there. There's only so much money to go around, so I have to stagger the build.
The issue is, the headers don't have an EGR provision, so I have to eliminate it. I didn't want to, just have to.
So far I have the front of the motor apart, the radiator out, the exhaust is gone, and the air system has been eliminated.
Another advantage to doing heads, is the headers should slip right in.
I got all new ARP bolts and it's being done right. The only two things I am keeping are the lifters and timing chain. They only have 32K miles.
I know.....I know.....but hey, everyone needs something to do.
I picked up a complete Super Ram that I'm going to install. Of course, can't have the Super Ram without the matching cam. Then of course, the heads are the weak spot, then the exhaust......and so it goes on.....
One of two things are going to happen. Either I can't get it to run (which really isn't going to happen) and I'll have to have you correct it.
Or, once I get it to run, I'll bring it up to you for tuning.
Once I decide on heads, I think AFR is a little to proud of their heads. I'm looking at Brodix and Patriot at this point. I hear what you're saying about compression. I can get 62CC heads which will put the compression at 9.5:1, the factory is 10.25. I've done all the math and feel pretty comfortable with that number. 9.5 is where the older L98s run. I can't find heads smaller than 62CC.
As far as the torque converter, that's my next step, after the engine work. Then a shift kit. At which point I take a breather and see what I like or don't. I'll go from there. There's only so much money to go around, so I have to stagger the build.
The issue is, the headers don't have an EGR provision, so I have to eliminate it. I didn't want to, just have to.
So far I have the front of the motor apart, the radiator out, the exhaust is gone, and the air system has been eliminated.
Another advantage to doing heads, is the headers should slip right in.
I got all new ARP bolts and it's being done right. The only two things I am keeping are the lifters and timing chain. They only have 32K miles.
Sounds like fun! BUT, remember....TOO MANY guys out there build em BACKWARDS!!! If you're thinking of a cam....Be smart and do the trans first cause without a converter you're gonna screw up the driveability by installing a cam.....
Do the trans first....then the cam.... You'll save money and have a car that's more fun to drive through the entire process.....
Also, the only reason that car makes torque is cause of the match of the compression and the intake.... Don't lower the compression.....That little engine NEEDS it!
Chuck CoW
Last edited by Chuck CoW; Sep 25, 2007 at 10:46 AM.
Race Director
Joined: Jun 2004
Posts: 13,956
Likes: 706
From: WI
What part do you think is BS? It looks like his year will throw a code but he did not put this cars year in the OP.
There are many here without EGR. (miniram has no EGR IIRC, same for LT4, also LT1 intake on L98, just to name a few of the more common intakes here) I have never read a post anywhere that someone had knock. If anyone knows of a thread with knock after EGR delete, I'd be interested in reading it. I'm not saying it's impossible but I have not read of anyone that did have trouble.
As for gas mileage, your single biggest issue there is how you drive.
Here are some other threads on deleting it:
http://forums.corvetteforum.com/show...40&forum_id=48
http://forums.corvetteforum.com/show...ght=delete+egr
http://forums.corvetteforum.com/show...ght=delete+egr
There are many here without EGR. (miniram has no EGR IIRC, same for LT4, also LT1 intake on L98, just to name a few of the more common intakes here) I have never read a post anywhere that someone had knock. If anyone knows of a thread with knock after EGR delete, I'd be interested in reading it. I'm not saying it's impossible but I have not read of anyone that did have trouble.
As for gas mileage, your single biggest issue there is how you drive.
Here are some other threads on deleting it:
http://forums.corvetteforum.com/show...40&forum_id=48
http://forums.corvetteforum.com/show...ght=delete+egr
http://forums.corvetteforum.com/show...ght=delete+egr
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 35,065
Likes: 0
From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
Sounds like fun! BUT, remember....TOO MANY guys out there build em BACKWARDS!!! If you're thinking of a cam....Be smart and do the trans first cause without a converter you're gonna screw up the driveability by installing a cam.....
Do the trans first....then the cam.... You'll save money and have a car that's more fun to drive through the entire process.....
Also, the only reason that car makes torque is cause of the match of the compression and the intake.... Don't lower the compression.....That little engine NEEDS it!
Chuck CoW
Do the trans first....then the cam.... You'll save money and have a car that's more fun to drive through the entire process.....
Also, the only reason that car makes torque is cause of the match of the compression and the intake.... Don't lower the compression.....That little engine NEEDS it!
Chuck CoW
Once the build is done, then it's a TC. Not too far after that.
Then we do a tune.
Then the shift kit.
Then we sit back and see if forced air is in the cards.
As far as the compression goes. Those heads are only 58CC the smallest heads out there are 62. On paper that's about 9.5 or just over it. That's not too much of a drop for the gains. Even after the compression loss I should be 100+ HP better.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by jsup
I am dropping the compression, as my heads are 58CC and I'm going to 64CC heads, that will drop compression by about 3/4 point to 9.5. By lowering the pressure, will that compensate somewhat?
pressures (and DCR) too much.
Originally Posted by jsup
As far as cyl temps, can't I put in a cooler plug. I think the car uses the AC R45 TSX. I can go to something like R43 TSX and lower the temp.
RACE ON!!!
Former Vendor
Joined: Nov 2005
Posts: 11,792
Likes: 255
From: Ossining New York
St. Jude Donor '07-'08-'09-'10-'12-'13-'14
Now, here's TWO opinions.....
YES. I wouldn't lower the compression ratio to eliminate the possibility of knock, but it appears you had already planned to for other reasons. The problem I see here, is that the combination of lowering the CR AND a bigger cam may lower your compression
pressures (and DCR) too much.
The heat range of the plug has little to no influence over combustion chamber temps. It has to do with PLUG temp.
RACE ON!!!
pressures (and DCR) too much.
The heat range of the plug has little to no influence over combustion chamber temps. It has to do with PLUG temp.
RACE ON!!!
Running this business, I've run into many customers armed with SUMMIT catalogs and the like who build their engines from HP ratings advertised in magazines and Summit books....
NO, the biggest carburetor you can fit WILL NOT MAKE THE MOST POWER....
Too many guys blow big money on fancy parts that are not right for them.... The best I can do for you is offer my opinion.... REMEMBER: I've been doing this for a living for 20 years and I've made the same mistakes you are making. I've also fixed HUNDREDS cars for guys that try to do the work and pick the parts themselves.
There is a right way....and a way that causes frustration and wastes money.... I'm trying to steer you the right direction....
Call me any time if you have questions.
Chuck CoW
:
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 35,065
Likes: 0
From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
YES. I wouldn't lower the compression ratio to eliminate the possibility of knock, but it appears you had already planned to for other reasons. The problem I see here, is that the combination of lowering the CR AND a bigger cam may lower your compression
pressures (and DCR) too much.
pressures (and DCR) too much.
As far as the cam, I'm matching it to the intake. 9.5 is right in the range of the older L98s.
What's DCR?
What do you think?
Team Owner
Joined: Sep 2001
Posts: 62,141
Likes: 1,729
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
I think you can live with static compression of 9.5ish, and just plan on new pistons for your next engine buildup when this one gets too old. You can try a thinner gasket to bump it up but otherwise without digging into the engine, theres nothing to do.
Race Director
Joined: Jun 2004
Posts: 13,956
Likes: 706
From: WI
You would lose probably 10ish HP and some minor MPG by decreasing the compression. My '88 year is 9.5 but I got some 1094 gaskets to increase the compression. Summit is showing they fit '90 too.
http://store.summitracing.com/partde...4&autoview=sku
http://store.summitracing.com/partde...4&autoview=sku
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Thread Starter
Team Owner
Joined: Oct 2004
Posts: 35,065
Likes: 0
From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
You would lose probably 10ish HP and some minor MPG by decreasing the compression. My '88 year is 9.5 but I got some 1094 gaskets to increase the compression. Summit is showing they fit '90 too.
http://store.summitracing.com/partde...4&autoview=sku
http://store.summitracing.com/partde...4&autoview=sku
Melting Slicks
Joined: Aug 2003
Posts: 3,394
Likes: 393
From: Lakeville MI
I think there is some merit to the EGR and knock discussion that was going on in some of the earlier posts.
Lately I've been working my timing table to reduce part throttle knock counts. In some cases I've had to reduce the advance down from the factory values in the vicinity of 46-48 degrees to more like 32 degrees for light loads and I still get a few knocks here and there.
I suspect that the EGR elimination is largely responsible for the knock counts that I've been trying to eliminate.
I can't confirm this, but it is the only explanation I can come up with to justify the behavior and what appears to be excessive factory spark advance for light loads. The spark table was obviously designed with EGR in mind. Something to consider.
Also regarding aftermarket heads: There is a 56cc aftermarket head that is largely overlooked. The trickflow 175 may be worth a look if you're interested in maintaining or increasing compression ratio.
Lately I've been working my timing table to reduce part throttle knock counts. In some cases I've had to reduce the advance down from the factory values in the vicinity of 46-48 degrees to more like 32 degrees for light loads and I still get a few knocks here and there.
I suspect that the EGR elimination is largely responsible for the knock counts that I've been trying to eliminate.
I can't confirm this, but it is the only explanation I can come up with to justify the behavior and what appears to be excessive factory spark advance for light loads. The spark table was obviously designed with EGR in mind. Something to consider.
Also regarding aftermarket heads: There is a 56cc aftermarket head that is largely overlooked. The trickflow 175 may be worth a look if you're interested in maintaining or increasing compression ratio.
Race Director
Joined: Jun 2004
Posts: 13,956
Likes: 706
From: WI
I think there is some merit to the EGR and knock discussion that was going on in some of the earlier posts.
Lately I've been working my timing table to reduce part throttle knock counts. In some cases I've had to reduce the advance down from the factory values in the vicinity of 46-48 degrees to more like 32 degrees for light loads and I still get a few knocks here and there.
I suspect that the EGR elimination is largely responsible for the knock counts that I've been trying to eliminate.
I can't confirm this, but it is the only explanation I can come up with to justify the behavior and what appears to be excessive factory spark advance for light loads. The spark table was obviously designed with EGR in mind. Something to consider.
Also regarding aftermarket heads: There is a 56cc aftermarket head that is largely overlooked. The trickflow 175 may be worth a look if you're interested in maintaining or increasing compression ratio.
Lately I've been working my timing table to reduce part throttle knock counts. In some cases I've had to reduce the advance down from the factory values in the vicinity of 46-48 degrees to more like 32 degrees for light loads and I still get a few knocks here and there.
I suspect that the EGR elimination is largely responsible for the knock counts that I've been trying to eliminate.
I can't confirm this, but it is the only explanation I can come up with to justify the behavior and what appears to be excessive factory spark advance for light loads. The spark table was obviously designed with EGR in mind. Something to consider.
Also regarding aftermarket heads: There is a 56cc aftermarket head that is largely overlooked. The trickflow 175 may be worth a look if you're interested in maintaining or increasing compression ratio.
Race Director
Joined: Jun 2004
Posts: 13,956
Likes: 706
From: WI
I wonder how tequilaboy's cam and the LT4 cam compare in that reguard. tequilaboy also does not have a stock cam, unless the knock counts he mentions was from a different car. I also wonder if the stock cam would have different knock.
