catalytic converters?

[rittenrotton 4]

I have a 70 coupe with a crate 302 and fast multiport efi...I have only put about 4,000 (+/-) miles on the motor but the exhaust smell is killing me. I have heard that adding catalytic converters to your exhaust will help to clean up the smell and not affect performance much. Just curious to hear some input about this..has anyone done this or know of a way to reduce the exhaust smell? 

[barnett468 418]

nope, it will simply change it to a different ignauseating smell.

look at your plugs, it may simply be too rich.

 

where do your tail pipes stop?

 

 

[rittenrotton 4]

Ok, I will have to take a look at them this afternoon.

You would think EFI would make it easy to have a fuel system run smoothly vs running to rich or lean lol

They go about 2" past the rear lower valance

[barnett468 418]

when do you smell the exhaust?

[rittenrotton 4]

I pretty much smell it all the time, whether I'm idling at a light, traffic or on the highway. I've checked the exhaust and headers for leaks using a wet dry vac on reverse and soapy water and found no leaks. I have also reset the efi computer to a new tune to see if that helps. But so far no luck..

[1969_Mach1 333]

You're right, in theory the EFI should have sufficient control the A/F mixture.  I'm not familiar with aftermarket EFI.  But from everything I read they are kind of primitive compared to OEM systems.  Aside from that, do you have a bad O2 sensor?  When the fail, they fail in a lean signal condition.  With increased valve overlap of performance cams, more unburned fuel enters the exhaust.  Thus, O2 sensors don't last as long and also cause strong exhaust smell that you cannot get rid of.  Are you using a cam designed for EFI?  They typically have a wider lobe separation angle.

If you put catalytic convertors on an overly rich running engine or engine with a large duration and larger valve overlap cam two thing will occur.  First like Barnett mentioned, the smell will be different but still very bad.  It will be a strong sulfur smell.  Second, you can overheat the convertor.  In one case back in the late 1980's I saw a convertor start a fire on an overly rich running new car.

[fvike 173]

2 hours ago, 1969_Mach1 said:

But from everything I read they are kind of primitive compared to OEM systems.

I read somewhere that the top EFI kits in the aftermarket today is basically early '90s OEM stuff.

 

[rittenrotton 4]

I wouldn't doubt that fvike...

 

I'll call thier tech support and see what they say but last time I spoke to them they seem surprised that it was running rich. 

 

I checked the plugs and they seemed good. I'm not sure about the sensors I mean they only have about 3000 miles on them and they're only about 3 years old. Can the sensors go bad that quick?

[rittenrotton 4]

I never knew that 1969_mach1, good to know 

[1969_Mach1 333]

That spark plug doesn't look bad from what we can see in the picture.  What does it look like on the inside, other than the electrode and tip of the porcelain?

Do you have any idea of the cam specs?  Just wondering if it's a condition that is not too rich but smells that way in the exhaust from a cam with a lot of valve overlap.

There are basically two categories of EFI, (1) Speed Density, this was the first type the U.S.A. OEM's developed and phased out in the late 1980's and maybe into the early 1990's.  And (2) Mass Air Flow which is still used today.  Basic difference is Mass Air Flow directly measures the amount of air entering the motor and Speed Density uses a combination of throttle position, engine RPM, and MAP (manifold absolute pressure) to determine how much air is entering the motor.  I'm not certain, but I think all the aftermarket EFI systems still use the early Speed Density Technology.  If I remember, one reason the OEM's made the change to Mass Air Flow was to get away from using a MAP signal as an input to determine the air flow entering the motor.

[rittenrotton 4]

The electrode and tip of the porcelain look clean and fine. 

I have the e303 cam and the specs are  a 220° intake duration at .050", and a 220° exhaust duration at .050". This E303 camshaft also features a 0.498" intake lift with 1.6 rockers and a lobe separation angle of 110°. 

 

I believe this EFI system has a Mass Air Flow sensor. 

[barnett468 418]

that plug looks like it may be a little rich if you used a flash in the photo or if you are using gas with ethanol. a plug color that used to look good is now considered to look slightly rich because the new gas burns a little cleaner, especially if it has ethanol.

also, no matter what you do, you will smell more exhaust with that cam than with a smaller cam.

 

 

[1969_Mach1 333]

Rare, but I do agree with Barnett on this one.  The E303 has 62 degree's valve overlap at 0.004" tappet lift.  You are going to have a rich smelling exhaust regardless of what you do.  You might be able to reduce it some, but it will always be there.  I use the X303 in a 351W and it also has 62 degree's valve overlap at 0.004" tappet lift.  The motor is carbureted, but it also has a rich smelling exhaust regardless of how I adjust the carb.  Doesn't bother me.

Was the E303 advertised as a cam for EFI?  I'd have to look through my Ford Racing catalog again.  If so, I'm sure Mass Air type of EFI would be better suited.

[barnett468 418]

54 minutes ago, 1969_Mach1 said:

Rare, but I do agree with Barnett on this one. 

...and on the rare occasions that you say you agree with me, I agree with that comment.

 

 

[rittenrotton 4]

I bought the motor as a Ford Racing Crate 306 and thats what came with the motor. I was more interested in getting a Holley Sniper but wad talked into this EFI system. AS far as gas, I use 93 octane pump gas., So its the gas that mucks up the plugs, regardless of whether or not the engine is running rich or lean? 

This is all new to me, so thanks for educating me! I appreciate all the help! 

[barnett468 418]

your gas does not have ethanol?

the gas does not "muck up the plugs". in todays world, all fuels burn cleaner than they used to due to additives, but even the old school gas from the 50's didn't muck up the plugs, it would just cause them to look darker than new gas does with the afr (air fuel ratios) being the same.

alcohol does not discolor the porcelain, and it is a cleaner, so the more alcohol a fuel has, the lighter color the plug will be with the same afr,  and with straight alcohol, the porcelain will not discolor much, if at all, therefore, you can't use the porcelain color as a guide for jetting on a vehicle that uses straight alcohol.

different fuels require different jetting to acquire the same afr.

the afr is regulated by the efi computer. the sensor in the exhaust constantly reads the afr and sends that info to the computer which then instantly adjusts the fuel to the level the computer is programmed to maintain it at.

even with that big of a camshaft, you should not be smelling exhaust inside the cabin when you are driving however, especially at higher speeds. it is possible that it is coming in thru the trunk seal even if the seal looks good. a pair of turn down exhaust tips might help a little. they are cheap at the auto parts stores and online

 

[1969_Mach1 333]

I will add, when I drive my Mach 1,  I don't get any exhaust gas smell in the cabin.

[rittenrotton 4]

The trunk seal is new, so that shouldn't be the issue, but I'll check it anyways...I will certainly add a pair of turn down exhaust tips and see if that helps any. 

[lanky 44]

If your tailpipes run out to the back, turndowns won't help the problem. Put simply there has to be a leak somewhere that allows you to the smell it while driving. 

You said you checked the exhaust and headers with a shopvac, did you test them together? Maybe the collector gasket/flange is causing it?

If your afr is rich, clean any efi sensors with sensor-safe cleaner, check for any leaks in intake tract. Where in exhaust system is o2 sensor placed?

[barnett468 418]

4 hours ago, rittenrotton said:

The trunk seal is new, so that shouldn't be the issue, but I'll check it anyways...I will certainly add a pair of turn down exhaust tips and see if that helps any. 

oh it can most certainly be part of the issue because the new trunk seals are nearly as hard as a rock and often don't seal well or completely.

[barnett468 418]

11 minutes ago, lanky said:

If your tailpipes run out to the back, turndowns won't help the problem.

Well I know for a fact from my first hand experience that turn downs can most certainly help the problem in some cases where the existing pipes extend straight out the back which is exactly why i suggested it as one option. 

 

 

[rittenrotton 4]

lanky - no I didn't test them together as I only have 1 shop vac. But I plugged the opposite muffler with a rubber glove and a zip tie while testing the other muffler with the shop vac and using soapy water. I didn't find any leaks, but I'm not sure how honest that method is. 

 

barnett468 - you could be right, most of these replacement parts are awful, the door seals seem to be longer than the originals and don't fit right. 

 

[1969_Mach1 333]

Back in the early 1980's my older brother had the problem of exhaust gases getting into the cabin on his 69 Mach 1.  That exhaust gas problem started after he cut off the tailpipes because one got crushed from the car going into a ditch (messing around and it got away from him).  Anyway, he learned that if he kept the kick panel air vents open, the cabin would pressurize a bit while the car is moving and it prevented the exhaust gases from getting in.  Not a good fix, but in a pinch it might be a temporary work around.  These cars were not so valuable back then and that's kind of how they were fixed. 

[lanky 44]

Barnett what I meant by my comment is that if he already has tailpipes and is smelling exhaust at highway speeds that changing the tailpipes setup won't help. Unless his current tailpipes end somewhat underneath the car/trunk. Yes changing the tailpipes can have an effect at idle or even lower speed cruising. 

[Desertdave 11]

On 10/19/2018 at 7:03 AM, rittenrotton said:

I have a 70 coupe with a crate 302 and fast multiport efi...I have only put about 4,000 (+/-) miles on the motor but the exhaust smell is killing me. I have heard that adding catalytic converters to your exhaust will help to clean up the smell and not affect performance much. Just curious to hear some input about this..has anyone done this or know of a way to reduce the exhaust smell? 

Just curious, what tranny do you have attached to that motor?