geronimo321

this is driving me nutts, if i tune my xl for top preformance, it tends to run hot.
if i richen it up to run cooler ,it seems sluggish and top end sounds like crap.
after lots of research, it seems i have a typical xl exhaust pipe problem.
what are my options to correct this, i've heard of the ofna 086, but i also the
ofna header will not work, and i will have to get a seperate header.
i have no idea what header, i will need, or if there is a better route to take.
as in diff pipe ,all together.

Revomad1

Pick up a CEN GST 7.7 pipe off Ebay and give it a shot. I'm running it on my K5.9 that I have in my Savage X SS. The CEN header can also be customized to work on the Savage. It is a larger diameter than the HPI header. Here's a video with the pipe only installed. http://www.youtube.com/watch?v=f69pCQ_DZZU . The truck was over geared for the Big Joe's, but it came alive when I installed the sand paddles! I have the header installed now also along with an XL 3 speed. The engine was still pretty fresh in the vid. It is making gobs of power and hitting higher rpm's now. The engine also runs a lot cooler than it did with the HPI pipe. I got my pipe for $11 including shipping. The 086 pipe is too small for a .36 engine. It was designed for .21-.28 engines. Here are some pics of the header and pipe installed. I cut 1/2" out of the middle and 1/2" off the end of the header. All those zip ties are holding the header together.

rclugnut10

My Feedback: (1)

if you have the XL the ofna header should work cuz you got the extra space behind the motor so you have plenty of clearance as opposed to the X needs a wired header to clear the shock

the lug

BudBud

Most of the headers I have tried work fine. I had to modify one to get it to lay down lower in the chassis.



I just ground a little off of the flange so I could turn it on the back of the engine. Bud

mountain_of_cheese

I like your wheels, what brand and model are they?

BudBud

[link=http://www.youtube.com/watch?v=yH9zai7zAKI]Ofna Pipe on a 5.9[/link] if you want to watch a video. Bud

BudBud

The .36 does not flow any more fuel than an Axial 32, LRP Spec 3 or Picco 28, the run times are almost identical in the Savage. It might make more power than the Axial, but the LRP and Piccos will out run it. I have not put an Axial 32 in an XL chassis yet, so I cannot really compare the two.



There is the Ofna style header in the XL chassis.



I think this is where the confusion started, I think, when you run the standard chassis, you need a header designed to work with the stock shock tower. The XL chassis has all the header room you will ever need. Bud

Revomad1

You can feed the K5.9 more fuel with the CEN pipe and it will make more power and run cooler. You have to run the 5.9 too lean with a smaller pipe for it to make power because they are too restrictive and they make the engine sound like it's running rich. The 5.9 will "breath" a lot better with the CEN pipe. Yes you need some back-pressure, but the CEN pipe provides more than enough, while the smaller pipes create too much back-pressure "smothering" the engine and making it bog down unless you run the engine too lean.
On a side note: Budbud, you need to find some dirt and catch some air with your savies!

Revomad1

I am running the CEN header because it is a larger diameter than anything else, not because I couldn't make anything else fit. I noticed a huge jump in bottom end torque and acceleration with the CEN header. I need to make a new video with my current setup.

Revomad1

If that is the best you can get out of the 5.9 as far as mid range power and peak RPM's are concerned, the CEN pipe+header combo will walk all over it. I also run my 5.9 without the venturi, which means the engine gets more air and more fuel, leading to more power.

BudBud

If you want me to put on a shorter tire that effectively cuts the gear ratio by a ton and make a video running through some sand or dirt so it is kicking up a huge trail of dust, I can do that.... I have watched those Cen pipe videos several times and do not see any huge power. The sandpit video is great and the truck looks quick with those paddles throwing sand all the time, but the speed is way down with the shrter tire.

Revomad1

Keep in mind that I had less than a gallon through my 5.9 in those videos, so it was far from making the power it is capable of now that I have about 2 gallons through it. Top speed is not a priority for me in a Savage. I get all the speed that I need now that I have an XL 3 speed though. I was using a 2 speed in that video with 17/47 gearing. Bottom end punch and acceleration is what I want out of a Savage. I get more of both with the CEN pipe. I get my speed fix with my Picco P3 .28 Street Revo running 22/34 gearing! lol. Budbud, I'm surprised you aren't willing to give the CEN pipe a try considering they can be had for less than $15 shipped. Surely you could fit that into your $1000/month R/C budget! (am I exaggerating or no?) lol. I'm sure you use your Picco powered trucks a lot more than the 5.9 trucks anyways. The Picco's are awesome, but I like the torque of the 5.9. I think I'm going to have to get my Picco modded so I can see what it's REALLY capable of.

BudBud

Actually, I run the two 5.9 trucks a lot because I let the boys drive them. I figure if somebody is going to do something stupid to destroy a engine, it might as well be a 5.9... good excuse for a Picco transplant!

They actually do make a lot of [link=http://www.youtube.com/watch?v=tVCLxpFJmTs]low end[/link] on the stock pipe. But they suck bad when you try to get rpm out of them and to get top end out of them, they get so stinking hot as you noted. The XL in that video is stock. pipe and all, well, it was at that time. It runs okay, but it has that huge dead spot in the upper rpm. The CEN pipe might give it more low end punch, its all good though, as long as we are having fun. Bud

Revomad1

Agreed! If nothing else, the CEN pipe makes the 5.9 run cooler. A cool engine is a happy and long lasting engine!

HPI_Savage_RC

I've used both pipes on the 5.9, and the 086 absolutely smokes the CEN GST7.7 pipe/header setup.

Excess backpressure is not the issue. It's quite the opposite.

roccos_van

My Feedback: (1)

Are you guys running the 086 pipe AND header combo or just the pipe with the stock header?

BudBud

The stock header is a silicone coupler. The Ofna pipe is a spring coupler. I have run them with the Ofna pipe and header, Tsais header, STS header, Hot Bodies Header, all to get different lengths. You can fine tune the engine by header length, basically it seems the shorter the header design, the higher up the rpm range the torque curve moves, a long header gives it more torque at a lower rpm. It is kind of cool to play with. Any of the spring style headers for a big block will work. I bought a whole series of headers from RC Hub just to play with the exhaust length. I have used them on several trucks since then and my variety pack has dwindled down. Bud

Revomad1

Did you remove the baffle but leave the cone in the CEN pipe? It comes with a baffle to control exhaust noise, but it limits performance. Remove the venturi from the 5.9 carb to allow more air and fuel into the engine. I noticed a big jump in power when I did this. It takes a bit of patience to master the tune with the CEN pipe on the 5.9 because it has to be run richer on both the low and high speed needles. If you have limited tuning skills, the CEN pipe is not for you.

black mamba

I pulled the carb insert out of mine too. I never run those things because all they do is just restrict air flow.

black mamba

I like the idea of running the CEN pipe because it was designed for a larger engine and I also like the fact that I can use my stock header with it. I'm all about bolt-ons. I'm going to hit up ebay and see what's out there.[8D]

Edit-I was running my 5.9 with 16/47, 3spd and Dirt Bonz, but I think I might go back to 17/47 with the CEN pipe. I know I should take the baffle out of it, but should I leave the cone in or remove that too?

black mamba

http://www.youtube.com/watch?v=f69pCQ_DZZU

I LOVE the roost man! Sweet.

Revomad1

Leave the cone in. It enhances performance, especially on the top end. I'm glad you liked the video. I know I had fun making it! When you throw the CEN pipe on, richen up your high speed needle 1/4-1/2 turn and work your way back down to peak performance. If you have trouble getting the idle to fall right away when you let off the throttle, richen up the low speed needle an 1/8 turn at a time until the idle drops quickly. Bottom end performance will suffer with the CEN pipe if the low speed needle is to lean.

black mamba

Cool, thanks for the tips. I'm bidding on a pipe right now.......................can't wait to get it in my hands.[8D]

HPI_Savage_RC

I'm not an idiot. I have been running nitro trucks for 4 years, and I certainly don't have "limited tuning skills". We tried every combination of setups possible. Baffle out and cone in did run the best, but it couldn't touch the 086 pipe/header in terms of mid to high RPM performance.

Based on the way you come across, I'm assuming you have never used any of the common buggy pipes on a 5.9. Try it. You'll ditch your CEN pipe within 10 minutes.

Also, removing the venturi will slightly increase top end power, but it will also dull throttle response and mid range acceleration by decreasing the airflow velocity into the engine. I run (or at least try to run) 8mm venturi inserts in all of my engines. This gives a good compromise.

Revomad1

I wasn't trying to imply that you had limited tuning skills, although when I read what I wrote I can understand that you may have taken it that way. I was merely warning those who have trouble getting a good tune. Throttle response is not a problem for me. I can spin all 4 tires on asphalt with my setup. I haven't seen a video of a 5.9 running strong on an 086 pipe yet, so please show me one. In the video that I saw, the 5.9 sounded like it was suffocating and it had nowhere near the throttle response that I'm getting with the CEN pipe. I couldn't care less if the 086 gets me an extra 2mph on the top end. When I'm bashing, I rarely hit 3rd gear, so I'll take stronger performance in the lower half of the RPM band any day over peak rpm's. Going as fast as possible on grass is not my thing. Raw torque and big air are what I want out of an R/C monster truck. If you're happy with the 086, that's fine, but don't discourage someone from trying a $10-$15 pipe and tell them a $50 pipe is the only way to go, because most would be happy with the cheaper setup. You will see increased gains if you use the CEN header also, because it is a larger diameter and flows better than the stock Savage header,