Has anyone done an actual dyno before and after with exhaust on a 6.2L

Fenix Mike · May 17, 2017

I have a 2010 Denali AWD 6.2L, and after building an exhaust on my buddies 6.2 Escalade, im not sure I want the possible drone or 10,000 mufflers when teamed with long tubes, so debating leaving my stock cat back on with the Kooks LTs. While most info ive found said +/- 5-10 rwhp with cat back, I realize very few are doing headers, THEN doing a before and after with a cat back so the gains may be skewed. I don't have a lot of free time and only get to use his shop here and there, so if its going to be a significant difference, id rather just get the exhaust knocked out while im doing the headers, but the older I get, the more I enjoy a nice quiet and relaxing ride.

I built some bitchin 3 inch true duals on his 2016 escalade that also has Kooks and a Whipple, but ended up having such severe drone that I had to do the large dual in/out magnaflow muffler AND two of the large chambered mufflers to make it tolerable inside (3rd attempt at making it "quiet"). Sounds like the end of the world at WOT, but I just don't want that much and IF its a minimal loss, im just going to install the headers and leave the exhaust stock. Ive been out of the performance game for a while, so other than tuning this truck and slapping an Airaid on it, I haven't done anything else.

Thank you

Fenix Mike · May 22, 2017

Well I guess we will find out. Headers will be here next week... it already moves pretty good with just an Airaid and tune, excited to see what these do!

XSKIER · May 22, 2017

I have pacesetter long tubes, off road y, and single 3" corsa touring cat back installed on my 07 AVY LS3. No drone, but it is seriously too loud. Anything above 3500 rpm it is really obnoxious, really poppy. I think that I may need to do something like your buddies escalade, but if you think maybe it is still too loud, maybe I'll throw a couple of cats back in too.

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Fenix Mike · May 22, 2017

I have pacesetter long tubes, off road y, and single 3" corsa touring cat back installed on my 07 AVY LS3. No drone, but it is seriously too loud. Anything above 3500 rpm it is really obnoxious, really poppy. I think that I may need to do something like your buddies escalade, but if you think maybe it is still too loud, maybe I'll throw a couple of cats back in too.

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My buddies truck is very quiet inside, just wakes the dead outside... I found the magnaflow chambered mufflers are significantly quieter than anything else, but I literally spent almost 4 hours building the mid section between all the mufflers, the overaxle pipes etc trying to make everything fit. I have pictures of the first version, but forgot to snap them after installing the huge cans. I was going to do the same setup on my truck, but since I don't have a blower (yet), I don't want to drop the $800 in steel and mufflers, and spend 7 hours under the truck in this heat building something for 10-15 horsepower at most unless I can see a dyno telling me otherwise. Being both of our trucks are AWD (mine and his), and only a couple AWD dynos in town, Ive just been doing street tunes on these.

Crobinson16 · May 23, 2017

What header size did you go with

Fenix Mike · May 23, 2017

What header size did you go with

1 7/8

Fenix Mike · May 24, 2017

Well, these showed up today...

Crobinson16 · May 25, 2017

They look nice what made you choose the 1 7/8 over the 1 3/4

Fenix Mike · May 25, 2017

They look nice what made you choose the 1 7/8 over the 1 3/4

18 years of being a mechanic, 16 of which were performance oriented. 1 7/8 are ALWAYS better. Period... I've Dyno proven it on anything GM builds even down to stock 5.7L F-body cars back in the day.

Crobinson16 · May 26, 2017

I can't see how a 6.2 in stock form or even tuned including a Cai benefits from 1 7/8 over an 1 3/4 header, yes in the 5500rpm range and up probably. There are other factors of collector length and primary length it self that can effect rpm range as well, if everything is the same between the two other than primary tube size, I feel sure it will loose on the bottom which is where most street or dd motors spend most of their time especially a truck that would benefit from the lower rpm tq. I haven't dynoed any of these motors so I can't say for sure which is better, I could very well be out in left field, but I have infact dnynoed our 410 sprit motors and the largest primary we run is 1 7/8 and 1 7/8 stepped to 2" for half mile tracks. Those motors flow far more CFM than the 6.2, plus it spends most it time at 8800 RPM with occasional lows in the 5800 to 6200 rpm depending on track condition. And when we switch to the larger stepped header it carries the power further in the rpm range but kills the lower Rpms, hence the use on larger tracks with higher corner speed. Nevertheless I was really hoping to see a dyno from someone who either did both sizes or even a dyno from two different people. That wouldn't be ideal but a chart from stock to 1 3/4 and than a different truck from stock to 1 7/8 even though its two different trucks as long as gearing is the same you would still see the gain given in rpm range between the two. I know that no two Dynos are the same but I'm not concerned about the peak number as much as I'm concerned as the rpm range the gain is made. I'd rather go with the 1 3/4 if they make more tq and hp say from 4500 Rpms and down that's great. Maby the 1 7/8 make more HP and tq. But if that gain is from 4500 or 5000 Rpms and up what's the point . I have a heavy truck that I tow occasionally with, not a light sports car that I take to the strip or track every weekend running in the upper Rpms.

Fenix Mike · May 26, 2017

I can't see how a 6.2 in stock form or even tuned including a Cai benefits from 1 7/8 over an 1 3/4 header, yes in the 5500rpm range and up probably. There are other factors of collector length and primary length it self that can effect rpm range as well, if everything is the same between the two other than primary tube size, I feel sure it will loose on the bottom which is where most street or dd motors spend most of their time especially a truck that would benefit from the lower rpm tq. I haven't dynoed any of these motors so I can't say for sure which is better, I could very well be out in left field, but I have infact dnynoed our 410 sprit motors and the largest primary we run is 1 7/8 and 1 7/8 stepped to 2" for half mile tracks. Those motors flow far more CFM than the 6.2, plus it spends most it time at 8800 RPM with occasional lows in the 5800 to 6200 rpm depending on track condition. And when we switch to the larger stepped header it carries the power further in the rpm range but kills the lower Rpms, hence the use on larger tracks with higher corner speed. Nevertheless I was really hoping to see a dyno from someone who either did both sizes or even a dyno from two different people. That wouldn't be ideal but a chart from stock to 1 3/4 and than a different truck from stock to 1 7/8 even though its two different trucks as long as gearing is the same you would still see the gain given in rpm range between the two. I know that no two Dynos are the same but I'm not concerned about the peak number as much as I'm concerned as the rpm range the gain is made. I'd rather go with the 1 3/4 if they make more tq and hp say from 4500 Rpms and down that's great. Maby the 1 7/8 make more HP and tq. But if that gain is from 4500 or 5000 Rpms and up what's the point . I have a heavy truck that I tow occasionally with, not a light sports car that I take to the strip or track every weekend running in the upper Rpms.

Multiple points against yours -

First off, you wont find a dyno in history showing back to back dynos of a LS based vehicle (not a sprint car, mustang, Honda or anything else) losing anything, anywhere, from opening up the exhaust on a quality pair of headers such as Kooks, American Racing, SW etc. Same generally applies to cat back as well as I did some pretty significant testing on factory exhaust vs cutouts vs true duals vs large true duals.

Second - dynos don't lie. "felt power", theories, or "it should" isn't scientific evidence proving anything. Fact is, while on a smaller cube LS engine the gains from 1 7/8 may be minimal over 1 3/4, they are still there, and there is no "loss" of low end, torque, or anything else through out the powerband. The larger the displacement and the more supporting mods you have, the more of a difference they make. The test mules for this theory back in the day were a 01 Camaro SS, 04 Z06 and 05 Z51. 3 different engines, all bolt on cars and all started with 1 3/4 as at the time sine 1 7/8 really weren't around then, some had fitment issues etc, and the minimal gain was about 8 rwhp. Is it a ton? no, but gains none the less.

Third - to carry on the 2nd point, should you run out and buy 1 7/8 headers if you have 1 3/4, and expect huge gains? No. I did it as a science experiment because I was able to sell the old headers to locals and had access to a dyno for free. On a 6.0 or larger its going to be about 10 rwhp at least more with the 1 7/8, so obviously not worth the investment unless youre going FI or internals on the engine. With that in mind, if you have not purchased headers yet, you would be silly to get 1 3/4 if both sizes were available. Years ago before long tubes were available on LS engines, we had shorty headers, and people swore up and down long tubes were a complete waste because shorty headers were fine. The same thing is happening now, and youre starting to see 2 inch primaries become common on our cars with cammed/stroked or boosted vehicles, or stepped combinations, leading to larger primaries.

Lastly - to touch on your final point of "If the gains are only 4500+ then whats the point", and the answer is simple. If it makes more power AT ALL, why wouldn't you do it if nothing else is given up? I challenge you to find a back to back dyno of the same vehicle with both sets of headers that lost mid range or low end torque. I wish I still had all my stuff from back in the day as id love to post it, but I don't.

Im not trying to attack you, just open your mind to 99% of opinion on forums is based on "I thinks" and "It shoulds", without any shred of evidence. 3 inch duals make more than 2.5s, 2.5 inch duals make more than a single 3, 1 7/8 headers make more than 1 3/4. LS1s LOVE airflow, and have really gone above and beyond with technology that takes advantage of extremely well flowing heads, lots of lift and relatively speaking, high revs. Any time you increase airflow in or out, these engines suck it up and make power. I understand your sprint car heads likely flow more, and rev higher, but its apples to oranges.

Crobinson16 · May 26, 2017

I don't even know where to start, you still haven't proved anything. Have you dnynoed 1 3/4 vs 1 7/8, back to back on a 6.2 truck version. Im pretty sure black bear has done it with Doug thorley try ys, thought it was 1 5/8 step and 1 7/8 step header not straight primary like arh or kooks.

A biger header "can" have a negitave effect on HP and tq, if the motor is not set up to accommodate the larger tube. I don't know where the drop off point is on a stock not internally modified 6.2 is I haven't dynoed or seen any charts posted yet.

You can fool yourself all you want, YES you can and will loose power if you have to big of header that is a proven fact, Don't take my word for it I'm just old Joe blow, call some of the most prestigious engine builders in the country. They do this for a living. To each their own I guess.

Crobinson16 · May 26, 2017

Here is a video that makes a good comparison for header size.

Fenix Mike · May 26, 2017

I don't even know where to start, you still haven't proved anything. Have you dnynoed 1 3/4 vs 1 7/8, back to back on a 6.2 truck version. Im pretty sure black bear has done it with Doug thorley try ys, thought it was 1 5/8 step and 1 7/8 step header not straight primary like arh or kooks.

A biger header "can" have a negitave effect on HP and tq, if the motor is not set up to accommodate the larger tube. I don't know where the drop off point is on a stock not internally modified 6.2 is I haven't dynoed or seen any charts posted yet.

You can fool yourself all you want, YES you can and will loose power if you have to big of header that is a proven fact, Don't take my word for it I'm just old Joe blow, call some of the most prestigious engine builders in the country. They do this for a living. To each their own I guess.

Since youre obviously offended that not only have I provided evidence I am correct (comparing your "I think" and "it should" by using sprint car examples, where as ive installed over 600 sets of headers since 1997 when the LS1 engine came out, and from just about every manufacturer), but youre also throwing irrelevant information and examples of engines, that again, aren't LS based, im going to tap out of the argument. Its a forum, everyone knows everything, and you can believe whatever you would like. As far as engine builders, I have quite a few of the "most prestigious" Lsx builders in my cell phone, your guess who they would agree with. Have a wonderful day, Craig, and im sure you wont be disappointed with the 1 3/4 headers, especially for what you do.

Crobinson16 · May 26, 2017

I'm I still do see your proof, surly you have a dyno run to show comparison of the two. I say I think and it should because I don't have proof myself of the 6.2 motor on a dyno with the two different sizes of headers. Offended no, not the least, I just don't like it when people say what they have done then no proof.

I decided to call both ARH and kooks to see what they had to say as they designed the headers, KOOKS says either will work but the 1 7/8 would carry hp further in the RPM but move the lower rpms tq range up, how far? He didn't say. He did state the 1 3/4 would have more tq and hp in the lower rpms and come on to the power better in the lower Rpms but not carry the hp as far as the 1 7/8. Now, Arh says 1 3/4 without a doubt is what should be in a NA 6.2 truck. Now he said if you have plans for forced induction then go 1 7/8. Take if for what it's worth.