Time to make it breathe

[Ron B.C]

As I wait for my fabulous and amazing women to do "her thing" with the next step of the interior remodel. I have some time to work on the engine and such. I have been looking at removing all the emission junk. I have done a few deletes on other older vehicles in the past. Is there anything special about a MH that I need to know?
1988 Itasca Suncruiser Chev 454

[geordi]

Originally Posted by Ron B.C

As I wait for my fabulous and amazing women to do "her thing" with the next step of the interior remodel. I have some time to work on the engine and such. I have been looking at removing all the emission junk. I have done a few deletes on other older vehicles in the past. Is there anything special about a MH that I need to know?

Bigger pipes need bigger tools...

What are you working on? Year / engine / etc? Older will be easier and have less stuff to remove for sure.

[Ron B.C]

Headers, exhaust etc will be done later. I need to make sure the women is happy with this unit we bought. Its the first class A I have owned and first camping vehicle she has ever owned. For now Ill just do the stuff that wont cost alot. Remove some of the choking emission stuff, re curve the distributor. Minor stuff

1988 Chev 454

[Solo_RV_Guy]

Originally Posted by Ron B.C

As I wait for my fabulous and amazing women to do "her thing" with the next step of the interior remodel. I have some time to work on the engine and such. I have been looking at removing all the emission junk. I have done a few deletes on other older vehicles in the past. Is there anything special about a MH that I need to know?
1988 Itasca Suncruiser Chev 454

It's yours and you can do whatever you want with it, but I think emission controls should be left in operational condition. Besides, in 1988 there wasn't a whole lot of them compared to current engines and I'm wondering what kind of "improvement" is worth spewing pollutants into the very air, land and water we RVers claim to enjoy.

[geordi]

Which makes less emissions:
Burning 10 gallons to go 50 miles, or burning 6 gallons to go 50 miles?

This is something that has always been puzzling to me. How people at the EPA can be otherwise so incredibly smart, but are completely clueless about the simple fact that making an engine FAR more efficient on fuel use guarantees less total emissions.

Every single change that is done to the engine itself rather than to the exhaust system external to the engine, every mandated "upgrade" in emissions design has resulted in engines that USE MORE FUEL to go the same distance. Being more efficient makes less emissions. Once you have maximized the efficiency of the engine, treat the exhaust as a separate entity and the result will be much better overall. On newer diesels, DEF is a post-engine solution that would be more effective without excessive EGR (causes more fuel usage). Catalytics are a good post-engine solution, but the vehicle in question likely does not have catalytics. It also does not (luckily) have EGR either.

[geordi]

Originally Posted by Ron B.C

Headers, exhaust etc will be done later. I need to make sure the women is happy with this unit we bought. Its the first class A I have owned and first camping vehicle she has ever owned. For now Ill just do the stuff that wont cost alot. Remove some of the choking emission stuff, re curve the distributor. Minor stuff

1988 Chev 454

You are lucky - I have a P30 chassis coach as well, in almost the same year. Mine is an 89 chassis / 90 body Holiday Rambler Alumalite, and I cut my teeth on modding / repairing that poor thing after Cruise America molested it for about 80k miles. (Never buy a former rental - we didn't know better at the time)

I talked with Banks engineers and they said that they couldn't sell me a single thing, I had already exceeded their best results. Original MPG was about 6, after I got done it was at 9mpg and that is with a 3-speed no overdrive and at 65mph.

The engine has (or had, depending on what is still there) like 4 V belts, dual engine-driven air pumps for the exhaust (these are the first things deleted), stock exhaust manifolds that are MASSIVELY restrictive, and a tiny carburetor. If yours is fuel injected, then that explains a few things on mine - I have a TON of unknown wires around the engine but nothing to connect to the engine other than the basics.

It took a while, but over time I replaced:
Carb with an Edelbrock 750cfm
Manifolds with dual headers, lost the useless H pipe and kept each bank fully separate.
Full length 3" exhaust pipe for each bank
Truck muffler for each bank, turnouts just forward of the rear tires - still 3"
Deleted the air pumps
Converted the front of the engine to Serpentine belt (this might be less advisable but it was many years ago that I did it and can't really remember why I did it)
Replaced clutch engine fan with fixed flex-blade fan.
My engine had 4 electric fans in addition to the driven fan, these are now wired to a relay and run full-time. Heat is a massive problem on these engines, keeping them cool is essential.
Cold air intake
Dual oxygen sensors (one per bank right at the header collector) wired to a single dash air/fuel gauge with a switch so I can see either left or right bank results.

I think cleaning out the exhaust lines and going to the 3" made the largest difference, the manifolds are just comically small on such a big motor. The amount of air this thing breathes is just staggering.

On the Edelbrock, I tuned it so that running down the road at 60-65mph the air/fuel gauge is reading right in the middle zone, basically perfectly stoichiometric and not lean or rich. While idling it does read lean, but that should be OK b/c it isn't under load and not pinging at all. The tuning is all mechanical and critical, but it ran beautifully like that until the ethanol gas went bad in storage and rotted the carb. I'm having an air leak problem right now so it is in storage and not really mobile.

[leadman]

Just so you know, it is a federal offense to remove or disable any emissions equipment on a vehicle no matter where you live, even if it is yours. That said, unless you have emissions testing in you area you probably won't get caught since the feds may never find out.
Here in Arizona when testing is done at the lab on 40th St in Phoenix the emissions from the tailpipe are bagged. Literally captured in a large bag and analyzed. Even though a vehicle may be using less fuel on the road it is possible for it to create more pollutants.
Yes, I was an Emissions inspector and a Fleet agent for the City of Phoenix.

I would not curve the distributor on an RV as they are designed to pull more on hills and such at close to WOT. Curving can lead to spark knock and the need for premium fuel. Removing an EGR can also lead to similar conditions. The air pumps help cool the exhaust manifolds as well as burn pollutants.
Red hot manifolds are not a good thing to have under the floor between the seats.

I had a 1988 Itasca 22' with the 454. All of the emissions equipment intact and operating and very low pollutant output. I was able to get 9 mpg on good flat road by using a vacuum gauge I installed in the dash as a guide. The higher the vacuum, the better the fuel mileage.

[Ron B.C]

Vehicles registered with antique plates and vehicles more than 25 years old with regular passenger plates must pass safety, but not emissions, tests. Motorcycles and vehicles older than 1975 are exempt from testing. Vehicles 25 years and older are exempt from testing.

This is a part from the motor vehicle act here in Canada. We dont have much for testing anymore and there has never been in the area I live. But I will inquire further about the laws pertaining to any removal of emission equipment.

[geordi]

I don't think anyone here is unaware of the Federal rules. Discussion of the performance and economy benefits is educational and what people discuss online may or may not have any bearing on what they do in real life.

That said - the benefits you state with regard to emissions equipment on this engine are minimal at best.

To my knowledge this engine does not have any form of EGR, and the rules are different anyway for medium duty chassis than they are for passenger vehicles. RVs on the P30 chassis would be considered medium duty. This would be why even as just about every passenger car engine had some form of EGR by the late 80s, medium duty trucks did not. My engine also did not have any form of PCV system, the valve covers simply have filter caps on them to vent to atmosphere. I do not know if this was from the factory or if the previous owner (Cruise America) did anything, but on this engine there was virtually nothing in the way of emissions equipment to remove.

No EGR, No PCV, the exhaust system was poorly designed and I do not recall if it ever had a catalytic converter. Certainly nothing like a modern engine.

The air pumps may force air into the manifolds, but this has little to do with "burning pollutants" as if the engine is tuned properly then there should be little that is actually burnable in the exhaust unless the engine is running rich for some reason. I agree that they instead likely are to try and reduce the overall temperature of the manifolds... BUT there is a tradeoff - they create more pressure in the exhaust, which by extension creates MORE of an air restriction and increases the EGT even more.

This is trying to patch a bullethole with a bandaid, rather than not getting shot in the first place. GM could have supplied the engine with much larger manifolds or actual headers that would have reduced the backpressure to a minimum... But that would have cost more. Would it have been cheaper to design the engine without expensive belt-driven air pump accessories, but with simple larger pipes from the exhaust ports? Likely... But that is a thought experiment only. We have to deal with the engines we have.

Your 9mpg sounds impressive on a stock engine... Until you declared that it was on a 22' coach. My 9mpg is on a 30' coach that likely weighs 150% of what your coach does. If you did the same upgrades that I did - simply opening up the exhaust, I suspect you would see the under-cover temperatures next to your seat drop by quite a lot - the EGT likely would drop by several hundred degrees all else being equal.

I remember working on the distributor on my engine as well, but I do not believe I set it for anything other than the stock advance and left it alone. This coach has been to the high desert and the climb to Kingman Arizona and does not ping... So I think it is happy as set. The exhaust while idling does not make your eyes burn (unburned hydrocarbons will do that if they are there!) and the A/F gauge is off the scale to the lean side while idling but there is no ping - so again, happy engine.

Any setup from a manufacturer is going to have compromises. I tend to believe that these compromises are worse when the manufacturer is only delivering a bare rolling chassis - we have the advantage that we can customize the engine precisely for the job it is being asked to do. Enabling it to breathe easier is the first and best thing you can do, second would be using an air fuel gauge and porting / jetting the carb so that it is bang-on in the perfect range while at steady highway cruise where RV's would spend most of their running time. The rest (hills, mountains) will sort themselves out based on that, and the economy will go way up.

[Solo_RV_Guy]

Originally Posted by geordi

Which makes less emissions:
Burning 10 gallons to go 50 miles, or burning 6 gallons to go 50 miles?

This is something that has always been puzzling to me. How people at the EPA can be otherwise so incredibly smart, but are completely clueless about the simple fact that making an engine FAR more efficient on fuel use guarantees less total emissions.

Every single change that is done to the engine itself rather than to the exhaust system external to the engine, every mandated "upgrade" in emissions design has resulted in engines that USE MORE FUEL to go the same distance. Being more efficient makes less emissions. Once you have maximized the efficiency of the engine, treat the exhaust as a separate entity and the result will be much better overall. On newer diesels, DEF is a post-engine solution that would be more effective without excessive EGR (causes more fuel usage). Catalytics are a good post-engine solution, but the vehicle in question likely does not have catalytics. It also does not (luckily) have EGR either.

DEF is a red herring, this is a gasser.


Funny but my daily driver pollutes far less per gallon, per mile, etc and gets 3x the miles per gallon of the '74 Camaro I used to drive. I'm not sure your analysis holds up as an absolute.

[EyezOpen]

This can be a touchy subject so anything i say is from experiences and opinions formed from those experiences. With that being said the overall all design of the 454 was centered around pollution and torque and that was accomplished thru head design and cam profiles. You are correct in the breathing aspect unforgettably no matter what you do the heads and cam mechanically limit air flow....Now you may tune up old parts that will aid in throttle response or maybe increase mpg by 1 mpg. but that about it.

However if you wish to tinker Google Peanut Port Heads Or Smog Cams..then theirs the intake.... and timing re curves... and of course valve train enhancements to live up to the new horsepower...

I do believe there is room for improvement in tire sizing however...aka changing the gearing to optimum engine efficiency but that would more than probably result in very poor performance in low speed driving or going up a incline...Sorry if this disappointing but ive built a few to many boat engines...great fun but really worthless unless you go big and dig into the fundamentals of the engine...Smiles doing that however is a easy 500 hp.

[leadman]

The stated 9 mpg for my 22' mh was achieved while towing a toad also.

The '88 P30 does have an egr and pcv from the factory. If the original air cleaner is still on the engine it should have a diagram and code for the emissions equipment it came with.

I also think most people are unaware of the Federal rules on altering emissions equipment.

[roccovw]

Any change made to improve engine breathing in one area will only be effective if changes are made in all areas related to engine breathing, if you change to headers you also need to change intake, cam and possibly the head to actually see improvements. Only time I would put headers on my motor home is if the manifolds were cracked and the cost of replacement is greater then a cost of headers. Luckily for me I have factory stainless manifolds on my 454 so they will stay on there.

[Ron B.C]

Thank you all for the responses, I certainly didn't mean to start such a debate!