Taking it to the extreme, what do top fuel dragsters use for headers? Are they just huge and going for the least restriction?

 

Hi guys,

I haven't been in one of these threads for a while. The trick is to keep the low end power with the larger primaries while still increasing the top end power with the bigger pipes.

We have been testing everything here at LGM for a while. Including stepped headers, plus 1 7/8 headers and even 2 inch. (forget the 2 inch)

the 1 7/8 headers as most are produced now don't allow the low end torque and hp numbers to stay up near the 1 3/4 headers. That was why we always went with the 1 3/4 headers on the road racing cars that we ran. We did have some success with stepped headers in road racing but that was with a 6 liter engine.

Our latest try with the 1 7/8 header on a 7 liter has been very promising. We have tried a couple of different configurations and a couple of different X pipe arrangements. At this point, to keep the torque up and still not lose the top rpm power, we had to come up with a completely custom merge collector combined with our X pipe location to achieve nearly exactly the low end numbers, and on top of that we exceeded the top power numbers of the best on the market to date.

We are only in the prototype stage but we should have our first production run complete by march. Our best numbers with our
own 1 7/8" LG Headers with our custom merge collector, on a stock 09 Z06 with a K&N filter has been 509rwhp and 483 of course with a tune.

These numbers actually exceed our old peak torque numbers BUT at the low rpm area, around 2-3000rpm, the 1 3/4 LG Pros still had between 10-15 ft lbs more torque but the high end hp numbers with our new 1 7/8 headers were up about 10+ from our old design and up from all the other brands that we used as our baselines.

Plus our power curve is really nice without a dip.

So from 3500 rpm up, our new design 1 7/8 header with special merge collector is equal or better than our LG Pros.

So you will have to decide what rpm range you are going to use every day and either plan for below 3500 rpm pulls off the corners or if you are going to be from 3500 to 7000 for your performance driving.


We have not tried the headers on an LS3 yet, but we will. Should be interesting but I think the 1 3/4 will be better suited for the smaller engines (but only a test will tell)


Thanks guys,

Lou Gigliotti

LGM

 

So LG is developing 1 7/8's with success on larger displacement.

Good to know

 

Damn, I'm glad I went with the 1 3/4'' headers on my Magnacharged LS2.

 

He has done this to a couple of my threads too. Must have a Napoleon complex.

 

Man, this is some controversial subject. Here a little fuel for the fire. Recent testing on the new ZR1 showed a 17 RWHP gain when switching from our 1-3/4" headers to our 1-7/8". Overall with very minor tuning the ZR1 gained 49rwhp and 60 rwtq of torque over the factory manifold set-up and that was with a loss of nearly 2lbs. of boost. These supercharged engines did not like 1-3/4" headers at all. On N/A LS3's 1-7/8" header systems have also proven extremely impressive throughout the entire RPM range. Particularly on LS3's I'll put our 1-7/8" header systems against anything 1-3/4" currently available or available in the future.

Nick

 

Nick, do you do heat coating at your shop?

 

Damn I love ARH's confidence.

49rwhp/60rwtq on an FI 6.2, awesome results

 

Has anyone ever compared header size on a deck top dyno?

 

Nope, I had A&A Corvette (ARH dealer) send mine out for coating. The back pressure reduced
was amazing from my old headers. I dropped like 60-70 db of turbine noise, from the blower in the car. Plus the thing pulls better.
but I went from 1 3/4 by 2 1/2 and to 1 7/8 by 3. the 2 1/2 oulet may restricted some along with the 1 3/4 . The cats flow more just by looking at the two.

 

I'm sure they do great against your 1 3/4 but can you please post some of these dyno results or track results instead of just the peak power. It would be helpful to see the curves and existing dyno's can be misleading.

Do you have a comment on GTOdoug's results posted in this thread and would you be willing to make me the same deal as LG did when I bought his headers? If I as a supporting tuner get a gain, I will keep them and pay for them. If not, I wont post the results and you take them back for a full refund. I have no agenda other than I want my car faster. I run 1 3/4 LG's with cats and would want cats on the 1 7/8.

The ZR1 is a 6.2 liter with a S/C not a stroker N/A. My car is a 6 liter making far more power than a ZR1 so they should work on my car big time.

 

And does that say what a 1 3/4 header would have done in comparrison? Once again, this is about area under the curve, not peak power gains that look impressive when you quote the numbers all on their own.

GTOdoug had great power from the 1 7/8 and then saw a 34rwtq gain under the curve from going to the smaller header on his 550rwhp stroker.

The final test for the above results would be to quote the new numbers with the smaller header.

 

They use open tuned length pipes. They are also winding out to a much higher rpm (up to 10k+) with an idle rpm in the 3000rpm range so I think the Tq at 3000 doesnt matter much.

 

 

IMO, you'd see a gain with the larger header. It's my understanding that with a boosted engine, exhaust back pressure relief is job one, scavenging not so much since the intake charge is already arriving under boost. The exception to this would be a turbocharged engine where the turbo relies on exhaust energy to drive it. Normally aspirated engines, of course, benefit greatly from scavenging so primary size is critical, meaning stay conservative to take advantage of scavenging in a usable rpm range for increased midrange torque.

 

Spin, I'll ask the Vette Doctors to get the dyno results together and post them. The 1-3/4" on the ZR1 were down across the board. I don't care what brand 1-3/4" headers were installed, the ZR1 requires 1-7/8" headers. With regards to your stroker, I know nothing about your combination but if you're producing more power than a ZR1, there's little doubt you'll pick-up substantially with an ARH 1-7/8" system. My suggestion to you is to order a set, pay for them, put them on and I'll refund your money if they don't improve your track times. Being that you're a supporting tuner and do this for a living, what you may learn may translate well for your customers.

Nick

 

No question that a boosted car needs the 1 7/8 header. As will a built 7 liter if the goal is peak power. And Our new LG Pro 7/8s have accomplished the power without the dip, so most all of the low end is in play.

The non boosted 6 liter is where the choice for low end or top end comes in to the picture.

As we have in the past, we have a new LG exclusive collector design and along with our X they seems to have helped the low end on our 1 7/8 headers.

As with all things Corvette forum related, time will tell and the numbers will be posted from all over the country.

Still looking at making a couple more changes before we go into full production.

Thanks

Lou Gigliotti

 

Peak torque rpm = Primary pipe area x 88,200 / displacement of one cylinder.

6.2L (380ci)/8 = 47.5 ci per cylinder

Primary pipe area = (3.1416) x (id radius) x (id radius), we obtain the following cross sections:

1 3⁄4 inches = 2.19 square inches;

1 7⁄8 inches = 2.53 square inches.

(assumes .040 header wall thickness).

Plug this info in the above equation and we get:

1 3/4 = 4066 rpm torque peak

1 7/8 = 4700 rpm torque peak.

Match your cam and other mods to optimize this.

Primary pipe length doesn't effect what value the torque peak number is or where that peak occurs, but it does effect what happens prior to torque peak and after. Shorter primary pipes extend the torque curve better past the torque peak while longer primary pipes extend the torque curve below the torque peak.

I haven't figured out how a merge collector changes any of this yet.

AFAIK, this equation applies to n/a engines only.

 

Generally we have found that the Merge Collectors broaden the curve before and after the torque peak. And the design of the merge, ie Angle of entry, length of entry, size of the choke, and the the angle leaving the choke etc.

All of these factors make a difference leading up to and after peak torque.

Thanks
LG

PS, Air Bus. Good calc.

 

Cars like mine and its power level are acheived with the same boost level of a lower powered FI car by using the benefits of a full H/C package before the s/c went on. A car with 10psi can be a 600rwhp car or hit over 700 like mine because they started with a H/C package making 100+ more HP before the s/c came into the equation. My cam isnt stock and lumping all FI cars into a single group and saying they have scavenging properties of less overlap assumes a stock cam and no superpowered car uses the stock cam. I have more overlap than the ZR1 and some H/C cars and make more power than the ZR1. I am still holding back until the forged motor is done shortly.

While a roots type blower is always making boost, a cenrtif s/c is not and a 6 liter in the midband is not making nearly the boost level that you would see on the ZR1 or a Mag so I will still disagree and stick with the fact that a centif s/c 6 liter or 6.2 liter will benefit from the added TQ in the 3k range where is it from from its peak boost. If you drive a car like mine with a boost gueage you will also see that so much of the driving when its not WOT is at 2500-4000 and still not making boost. This means that the low end grunt from headers is very much an issue. So if not making boost and there is a 30rwtq jump at 3k, the car will feel more lively. One of the biggest complaints I have is how the car feels off boost compared to when it was N/A. The throttle sharpness took a hit and any TQ loss down low would compound this issue. I could care less about a 15hp gain up top if the car was anymore of a slug off boost. I cant stress that last sentence enough. I dont go around flooring my car all over the place. Somewtimes I roll into the throttle with no boost thinking the fun at part throttle is gone. Until the blow off valve stops letting the boost vent and makes boost, the car is slower than it was n/a and it needs all the help it can get. I guess the only way to say this is that off boost a centrif s/c car is N/A until the BOV closes which is the vast majority of your normal driving when low end TQ matters so much. Its is worse than N/a. Cars that didnt have a H/C job before the s/c wouldnt notice this as much nor would a boosted stroker.

Turbo cars dont use headers.