new RVowner Posted July 19, 2015 Share Posted July 19, 2015 (edited) would it help at alll with the horse power & mpg if we put 2.25 inch exhaust pipe in our 1984 toyota rader rv?Or would it help or hurt with the performance at all?we have 1 3/4" stock pipe & muffler on there nowthank you. Edited July 19, 2015 by new RVowner Quote Link to comment Share on other sites More sharing options...
WME Posted July 19, 2015 Share Posted July 19, 2015 Yes, but how much, who kows Quote Link to comment Share on other sites More sharing options...
Derek up North Posted July 19, 2015 Share Posted July 19, 2015 Yes, no, maybe. Only your hairdresser (with a rolling road) knows for sure. Quote Link to comment Share on other sites More sharing options...
fred heath Posted July 19, 2015 Share Posted July 19, 2015 Why do you want to change your existing system? The potential gain in HP would be minimal in relation to the cost of the upgrade. Normal rule of thumb is your exhaust pipe should be the same diameter as the exhaust manifold collector. To do the conversion your talking about would involve a complete custom fabricated exhaust system. I recently upgraded my 1979 from 1 7/8 to 2". I was fortunate to have access to a pipe bending machine. I did this because my existing exhaust system needed replacement anyway. As far as any increase in HP, I've observed none. Keep in mind once you go custom, you can no longer run to the parts store for a new muffler. My advice is stay with your stock system. You can gets parts anywhere. :-) Quote Link to comment Share on other sites More sharing options...
new RVowner Posted July 20, 2015 Author Share Posted July 20, 2015 (edited) Thank you for the opinions guys The cat and everything back is all junk and has to be removed anyway. So i was wondering if i went to 2 1/4 instead i might gain 1 or 2 HP for the freeway.As all of you know, These toyota rader motorhomes have 22r engine in the older ones and i love these little buggers, You can beat that engine with a stick and it just keeps going, But they don't have much power at all for the task that they have to do with a house on their shoulders, and i figured 1 or 2 HP might help a little on the freeway. lolnote: Going from 1 7/8" to 2" is almost nothing compared to changing it from 1 3/4" to 2 1/4"(That would be 1/8" to 1/2") <---- that's eight times the size increase that you had so maybe it would help on the freeway to get that air out of that little engine ?!?!?!?I was thinking of just running straight pipe to the muffler and call it a day (2 1/4" or 2 /1/2") + NO CAT What do you guys think? Edited July 20, 2015 by new RVowner Quote Link to comment Share on other sites More sharing options...
fred heath Posted July 20, 2015 Share Posted July 20, 2015 My motor is the 20R. My exhaust manifold down pipe is 2" I.D. It transitioned via flange to 1 7/8 for the remaining exhaust system. For me to put larger pipe could actually have an adverse effect on engine performance. This is do to an action called "scavenging". You can research this info online for a better understanding. Bigger is not always better. If your going to rip the entire exhaust system off, do whatever makes you happy. :-) Quote Link to comment Share on other sites More sharing options...
WME Posted July 20, 2015 Share Posted July 20, 2015 My system...stock to cat converter, then 2" to muffler, then 2.25" for the rest. Reason is that the local muffler shop doesn't have a mandrel bender. The bender they have reduces the cross section a bit in the corners. Quote Link to comment Share on other sites More sharing options...
new RVowner Posted July 22, 2015 Author Share Posted July 22, 2015 (edited) My system...stock to cat converter, then 2" to muffler, then 2.25" for the rest. Reason is that the local muffler shop doesn't have a mandrel bender. The bender they have reduces the cross section a bit in the corners. What kind of mpg are you getting with that setup? Mine has always gotten around 15mpg (The best i ever had was 16.5mpg) And that was with a cat with holes in it and a muffler that was falling off. What a 22r get better mpg and horse power just running straight pipe. (i know, it would be very loud) but i was just wondering. Setup: 1984 toyota 22r manual 4 speed Edited July 22, 2015 by new RVowner Quote Link to comment Share on other sites More sharing options...
zero Posted July 22, 2015 Share Posted July 22, 2015 would it help at alll with the horse power & mpg if we put 2.25 inch exhaust pipe in our 1984 toyota rader rv? Or would it help or hurt with the performance at all? we have 1 3/4" stock pipe & muffler on there now thank you. I doubt it would make any difference in normal-range power and I'm sure it would have no affect on fuel mileage. A 2.4 liter engine doesn't need much flow, in the air intake, or out the exhaust when running 2800-3200 RPM most of the time. I've heard (and read) the many inflated claims about power increases by changing exhausts systems and air intakes. Very few actually gain anything unless you drive a lot @ 5000-7000 RPMs. My 446 cubic inch turbo-diesel on my Ford truck came with a 2.5" single exhaust from the factory. When it finally fell apart, I put a 4" exhaust on since it had to be replaced anyway. Made absolutely NO difference in power or fuel mileage. Same for many other rigs I've had experience with. If my 446 cubic inch engine with forced induction (turbo) does fine with a 2.5" exhaust - seems your 144 cubic inch Toyota with NO turbo has more then it needs with a 1 3/4" exhaust. By the way - one other sort-of test. My 1985 Ford F250 with a 6.9 diesel. The exhaust system fell off of it completely and it just sounded lousy. Fuel mileage and power was exactly the same. Quote Link to comment Share on other sites More sharing options...
zero Posted July 22, 2015 Share Posted July 22, 2015 A few added facts. The 22R or 22RE Toyota has an intake system with a max flow of around 325-330 CFM. 150-200 CFM when doing normal crusing on the highway. A 1 3/4" exhaust pipe has a flow-rate of around 240 CFM. A 2" exhaust pipe has a flow rate of around 320 CFM. A 2 1/4" exhaust pipe has a flow rate of around 400 CFM. So, in theory - if you drive your Toyota RV with the engine at the absolute max - there is a slight gain with a bigger exhaust. With normal driving, none. Quote Link to comment Share on other sites More sharing options...
new RVowner Posted July 22, 2015 Author Share Posted July 22, 2015 A few added facts. The 22R or 22RE Toyota has an intake system with a max flow of around 325-330 CFM. 150-200 CFM when doing normal crusing on the highway. A 1 3/4" exhaust pipe has a flow-rate of around 240 CFM. A 2" exhaust pipe has a flow rate of around 320 CFM. A 2 1/4" exhaust pipe has a flow rate of around 400 CFM. So, in theory - if you drive your Toyota RV with the engine at the absolute max - there is a slight gain with a bigger exhaust. With normal driving, none. Thank you. That was some info i was looking for. We cruise this little mini at 60-65 and it runs fine. with that info, do you think that would help the engine at those speeds? Quote Link to comment Share on other sites More sharing options...
zero Posted July 22, 2015 Share Posted July 22, 2015 Thank you. That was some info i was looking for. We cruise this little mini at 60-65 and it runs fine. with that info, do you think that would help the engine at those speeds? Cold denser air into the intake amounts to less CFM then the hot exhaust. Standard engine-math says a 144 cubic inch gas engine (22RE or 22R) flow 363K CFM @ 3500 RPM (65 MPH in an RV with auto trans). Toyota engineering says the 22R or 22RE head has a max flow rate of 271 CFM (intake). So I don't know which numbers to go by. Using the 363 CFM at the cool intake - exhaust flow (1000 degrees F) at 3600 RPM would be 981K CFM. Using the Toyota intake flow figure of 271 CFM, exhaust flow (1000 degrees F) would be 732K CFM. So just going by the math, there should be some improvement with a bigger exhaust. I've never noticed any, but who knows? I just drove my 1978 Chinook 80 miles with no exhaust system at all and power-wise - it felt no different to me. Not exactly a scientific test though. Quote Link to comment Share on other sites More sharing options...
zero Posted July 22, 2015 Share Posted July 22, 2015 By the way, other, simpler math gives different figures which I tend to believe more. Why? Toyota has a lot more at stake to get the math right then I do and I don't believe they'd install an exhaust system that would rob power from the engine. Yeah, I know - aftermarket parts sellers always say different. Other math says this: 2.2 CFM of exhaust needed for each horsepower 22R – max 108 HP – needs 237 CFM of exhaust flow 22RE – max 114 HP – needs 250 CFM of exhaust flow Toyota 1 ¾” exhaust – 2.4 square inches, 276 CFM if straight. A little less with curves. So according to this - the stock Toyota 1 3/4" system is more then adequate for anything a stock engine can spit out. Quote Link to comment Share on other sites More sharing options...
WME Posted July 22, 2015 Share Posted July 22, 2015 One other thing I did was to use a muffler from a Ford P/U with a single exhaust and a 460 cid engine. Very quiet, a mellow tone and no back pressure Quote Link to comment Share on other sites More sharing options...
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