Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 11, 2025 ...

Slow take off from stop. Exhaust Mods?

December 15, 2020, 07:12:21 pm

Has anyone had any experience with replacing the muffler with a resonator on a 3208T Cat? If so, Did it help low end acceleration? Our coach has always been lacking in acceleration but as soon as she builds up a head of steam, runs fine. I read extensively in the forums archive on this but did not see anything on the 3208T Cat.....

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Re: Slow take off from stop. Exhaust Mods?

Reply #1 – December 15, 2020, 08:00:13 pm

I had the same problem I found my was very Lazy on  takeoff once it was rolling, it roll along tel I hit a good hill and labour up it slow but sure It was like that from the time I bought it. I ask about it on the form and they told me it was a motor home not a sports car This fall I had to do radiator in it and I got the  air cooler check  at the same time it was leaking and that was my problem it was like night and day I would get yours  check.  Check your engine boost  if the CAC is leaking you will lose power they crack from twisting

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Re: Slow take off from stop. Exhaust Mods?

Reply #2 – December 15, 2020, 08:11:31 pm

Your injection pump may be in the "no smoke" position. Some, especially the electronic engines don't fuel the engine much until there is some boost. So, perhaps a sensor is bad. Detroit have this problem but they are electronic. A simple resistor does the job on a 6V-92.

Perhaps there is a CAT specialist on the forum that can help. Also, check your boost at low RPM. A leak in your intercooler can drop the boost on the low end. Low fueling off the line means slow acceleration.

Pierce

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Re: Slow take off from stop. Exhaust Mods?

Reply #3 – December 15, 2020, 08:45:19 pm

No CAC on a 3208.
I'm sure someone will chime in, personally the, drive it like a house advice is my approach. It's not hard to get out of order with a vehicle this size as they aren't as nimble as ......anything else. To paraphrase " there are old pilots and bold pilots, but NO old bold pilots.

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Reply #4 – December 15, 2020, 09:06:02 pm

Twenty years a had a Kenworth T300 with a custom extended cab, a 12 ft box and set up to pull a big custom three axel travel trailer. Our GCVW was about 35,000 lbs. We had a CAT 3208 with 275 ho through a 9 speed and heated up the rear end. That engine had go, usually began in second or third gear and was never the slowest off a stop light, it had a great 0 to 60, at 60 with the turbo wound up you had to be careful or you would be up in the high 80's n seconds. I know people badmouth CAT but not me, that was one bad ass small engine that never gave me a moments trouble all the time I had it. So I would thing you may go and spend a while on a dyno and check it out.
Now we have the 350 Cummins in our 99 36' and love it, don't know if this helps.

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Re: Slow take off from stop. Exhaust Mods?

Reply #5 – December 15, 2020, 09:10:57 pm

I turned my fuel up and cut the muffler off for more power . Lost 1 mpg.  I have since turned the fuel back down to stock. It puts out black smoke on throttle tip in and clears out  as revs build . It should smoke a little just off idle. If yours does not , and the  safety wire is intact on the fuel pump, maybe  turn it 1 bolt and see what happens.  I found my bus is plenty fast for me.  It does not rip  from the light .
  The  resonator  is from summit racing .  Might be 4 in  x 4 in.  or 5x5 .  Some turns /pipe and strap from NAPA plus a clamp completes the package.
Other mods; I turned the rpm limit up one turn  . It pulls to 2600 if I need it to . Good for hills in 3 rd gear. I never mat it hard at 2500 or over. 
I  moved the down shift cable looser so that it may some times up shift sooner at part throttle .
  It gets a solid  10.5 MPG here in FL( pulling my little trailer3200#).  Not many hills.    Cruise @ 2200.

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Re: Slow take off from stop. Exhaust Mods?

Reply #6 – December 15, 2020, 10:00:14 pm

Now I have a completely different engine but when I had my turbo rebuilt I noticed a huge difference when taking off from a stop.  I had the turbo done because I was hearing an intermittent bearing like whine, not because it felt slow.  It must have lost performance gradually because I didn't realize it. 

I would check the boost pressure and do some research to find out what it should be for that engine and horsepower.  The Wanderlodge owners group might have such info. 
This is what I found with a quick search: Normal Max Turbo Boost on 250 HP 3208 - Wanderlodge Owners Group
Or this one: 3208 boost

I would rig up a test gauge with tubing up to the dash.  I would use copper tubing for the first couple of feet due to engine heat.
There is usually a pressure tap somewhere on the manifold.  Another symptom of low boost is more black smoke than usual.

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Re: Slow take off from stop. Exhaust Mods?

Reply #7 – December 15, 2020, 11:35:47 pm

"No smoke" is usually a setting that limits the fuel coming off a stop sign or traffic light. With limited fuel, the engine can't produce much power so does not spin up the turbo quickly so it lags across the intersection. With more fuel, the turbo spins up quicker and you are across the intersection quicker but at the expense of a little black smoke out the exhaust.

A failing turbo copies this condition. If the turbo wears enough, the seals may fail and allow oil into the intake and raise the EGTs. You see this in race cars where the turbo seals fail, the EGTs go up and that melts a hole in the piston crown.

Pierce

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Reply #8 – December 16, 2020, 08:17:42 am

My previous coach (U280) was sluggish on grades and start ups. I turned up the fuel a bit on the 3208 Cat made it much more enjoyable to drive. Didn't make it a habit to use the extra power but was nice to know it was there when needed.

https://www.thedieselgarage.com/threads/turn-up-fuel-and-rpm-on-a-3208-cat.7294/

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Re: Slow take off from stop. Exhaust Mods?

Reply #9 – December 16, 2020, 10:51:57 am

Easy cure for Detroit 2 cycle owners with only a resistor needed: Poor Acceleration from a stop / DDEC I II III IV / smoke control / Fix ??

For 4 speed owners, first gear is much taller than first in a six speed (4.xx vs 6.xx). I followed a U320 36 with a M11 for a distance. I thought that we were a tiny bit quicker up some hills where we had a good ratio but from a stop, the U320 was half way down the block before we were across the intersection. In our case, it's not only the tall ratio in first but the smoke control in the ECU. This becomes worse up at high altitude.

We are geared for 82 mph at fuel cutoff in 4th so having 4 speeds leaves a big gap (RPM drop) between gears and handicaps the engine. The 6 speed does make a world of difference.

Pierce

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Re: Slow take off from stop. Exhaust Mods?

Reply #10 – December 16, 2020, 11:37:43 am

Might check to see if the air throttle is fully stroking the injector pump "open". Have you installed a new air filter? Filter minder guage may not be functional. Any soot in engine bay that may indicate a bad exhaust manifold gasket which would limit boost. From your emails and top speed less than 70 I'm thinking your short on power for some reason.

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Re: Slow take off from stop. Exhaust Mods?

Reply #11 – December 16, 2020, 01:53:24 pm

Mine pulls to 78mph @ 2550

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Reply #12 – December 16, 2020, 02:00:04 pm

82 mph @ 2130

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Reply #13 – December 16, 2020, 02:44:22 pm

83@ 2650

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Reply #14 – December 16, 2020, 02:44:49 pm

Here's the Bus Grease Monkey's (Scott Crosby) Screaming Jimmy 6-71  tuned up to 2650 rpms with a resonator. 

He travels in it and and works on vintage busses.  He has some amazing videos keeping these old busses on the road!

Jerry

https://www.youtube.com/watch?v=KMVO_5w53Ok

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Re: Slow take off from stop. Exhaust Mods?

Reply #15 – December 16, 2020, 04:56:24 pm

God I love this forum!!! I am going to be sure about,of course, that first I have a clean air filter, and second, that I dont have any turbo related exhaust leaks, nor a weak turbo itself. Then, after that is squared away, some pump adjustments are in order, and a 5x5 resonator be next. Thanks for all the info. I'm an old drag racer, I campaigned a 1966 Chevelle SS 396 360HP to a national record holder back in the 70's, and did it on a shoestring..... Now I'm going to learn how to hot rod a Cat on a shoestring. COOL!!!!

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Re: Slow take off from stop. Exhaust Mods?

Reply #16 – December 16, 2020, 07:39:52 pm

Your going to want and need some sound so do the resonator.

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