Why am I getting so many exhaust fumes?

[traveler501]

hi, guys

I just got my car, and after rejetting for altitude, took it for a

warmup, then made some adjustments, one more short trip and

parked it. I had the hood and nose off the car all this time.

And both the crankcase breather and valve cover vent into the

atmosphere at present. Long story short, I swallowed a lot of

fumes…kind of made me sick. And I'd like to avoid that in

the future.

 

I'll show a couple pics…I'm just curious if there's anything

obvious I'm doing wrong. Is my exhaust tip too close to the

back of the front wing and getting turbulence while driving?

Is driving without the nose and hood on screwing up the airflow?

Also, it was worst at idle…would I be better off with a narrow outlet

pipe to "jet" the exhaust farther away? Should I get that

exhaust a lot farther away from the car? How much of this

is because the crankcase/valve cover breathers aren't hooked

to a can or vacuum source?

 

I'm interested in any and all thoughts. This is one of those

things I'd like to get right the first time! And I have no problem

with overkill *grin*

 

thanks in advance,

John

 

Edited December 7, 2015 by traveler501

[slomove]

Not sure if the clam shells contribute to the situation, but I suspect the side exit is just too short. Usually they end right in font of the rear wing so that the exhaust gas is blown clear off the side of the rear wheel. I your case, the exhaust gas may get caught up in the turbulence of the rear wing and some of it get into the cockpit.

 

Quite often drivers opt for the side exhaust in spite of the noise because it make less of a stink than a rear exit exhaust, which is known to pull back fumes over the boot.

 

I have the crankcase and valve cover breather into the air (via catch can) and no problems, but that may depend on how much blow-by your engine makes.

[traveler501]

Thanks, it would be easy to swap in a longer mid pipe and get that exhaust tip near the rear wheel.

I'm curious if anyone else is having problems….does it pretty much always work just moving the

exit point further back? That would be an easy fix…thanks, slomove.

[Croc]

I think Gert has the answer - the side pipe should be extended further rearwards and then slightly further out in front of the wing so it does not get scooped up and back into the cockpit. The side exit is better than rear exit for avoiding fumes.

[traveler501]

Thanks, guys, I'll move forward then with a rearward exit, similar to the 160 photo attached. I'm going to drop

this whole BSA setup from the header back. Is there a good source for traditional Caterham parts in the US?

Or would any "round can" muffler work? Meanwhile, I'll start looking around…I'm assuming I'll need a

custom mid-pipe made locally and some new mounts. Pretty excited about getting back on the road!

 

thanks again,

John

Edited December 7, 2015 by traveler501

[Off Road SHO]

John,

 

I'm no aerodynamics major, but if you are going to make a new pipe and muffler, I would put the muffler up closer to the header down pipe and have a longer exit pipe. This would give the exhaust gases more time to settle back down into a nice laminar flow before they exit the tip, giving them more speed and less burbling. I also would not flare the tip. When someone on LOCOSTUSA did an airstream model on the Seven bodywork, I was amazed at how much of the air that hits the rear fenders flows up into the cab rather than off to the side.

 

Tom

[anthonyseven]

My old Birkin came with a rear-exit exhaust, which was the worst. The fumes would be pulled up over the boot from the rear and into the cockpit. The smell settled in my hair/hat and jacket/shirt around my neck and shoulders.

 

You want to direct the exhaust both down and out, to prevent it from coming up over the rear wing from the side, or beneath the car and up over the boot from the rear.

[traveler501]

ok, what I've got so far is: down and out, further out laterally past the rear wing, and laminar flow. Also I'm following

up on Tom's info about LOCOSTUSA's airstream models. I've found some CFD models for the front of the car, hoping

to find some 3D models of the rear (!) I'll start researching muffler options today too. All of these comments have

been extremely helpful. Extra thanks to Tom and Mike for coming through for me a couple times now!

 

John

[scannon]

I'm in agreement with the outlet just in front of the rear wheel and pointing out. I used a Magnaflow muffler that has internal insulation. Unless it sits and heat soaks I can put my bare hand on it driving down the road on a hot day and not burn it. It is warm but not blistering hot like the turnout at the end. I don't get any exhaust smell in the cockpit unless I am stopped and the wind is blowing from the rear and driver side of the car.

 

[traveler501]

hi, Skip

Thanks for the pic and the info…that setup would pretty much bolt right

up to mine (weld a clip to the muffler and I'm good to go!). And I like the

insulated aspect so I can get the can nice and close to the bodywork. I'm

sure I can track it down…but would you have any clues which Magnaflow

you used?

 

thanks,

John

[scannon]

I'm

sure I can track it down…but would you have any clues which Magnaflow

you used?

 

thanks,

John

 

I was afraid you were going to ask that. I can't recall the model number and am not good at saving receipts. Most but not all of them get stuffed in a file drawer along with all the other car receipts. I'll have a look and let you know what I find.

 

Edit: I am amazed, I was able to find the receipt for the muffler. I only had to sort through half a drawer to find it.

 

Magnaflow #12649. This is a 3" inlet and outlet muffler so a part number for different inlet and/or outlet will have a different number but it will get you in the ball park.

 

https://www.magnaflow.com/products?partNumber=12649

Edited December 8, 2015 by scannon
Add part number

[traveler501]

hi, Skip

Outstanding news, thanks….i will jump all over this. Thanks to everyone for making this

much, much easier than I was expecting. I really appreciate all the help and support.

I look forward to being able to offer some help in return one of these days….

 

cheers,

John

[maurice1]

Hi John

Don't weld a tab, clip etc. to the muffler as it will fatigue and break. Trust me I know and as an Aircraft Welder Tradesmen I understand why.

the best solution is to roll a strap of steel to fit the muffler diameter or to fit the tailpipe diameter, fold a small tab on this to bolt up to the chassis with a rubber exhaust pad between the brackets.

My first welded tab on my Birkin exhaust broke within a year, my repair as above has lasted 4 1/2 years and still going strong.

I have read posts in the past about rear exit tailpipes on 7s causing fumes in the cockpit but I have never experienced this on my rear exit exhaust. It certainly makes for a quieter cockpit on long drives.

cheers

Maurice

Edited December 9, 2015 by maurice1

[coffee break]

+1 on the clamping is better than welding.

I have my exhaust exiting behind the rear wheel. pointing sideways. I haven't experienced any fumes when doorless. I have noticed some since I have made some doors, but not too bad.

[scannon]

I have a second exhaust system that exits out the back using a pair of OEM Caterham tail pipes. There is a splitter behind the muffler to take it from one 3" pipe to the two 2 1/4" Caterham tailpipes. With the windshield on but no doors there is a little exhaust smell in the cockpit. Put on the side curtains or the bikini top and it gets very bad in there. I only use the rear exit system with the Brookland screens installed, no problem in that configuration.

 

There is a third system which is simply a 3" pipe with no muffler and a side exit. It is so f...ing loud that even with ear plugs and a helmet its uncomfortable on the track and cop bait on the street. You would think the turbo would have mellowed the noise a bit.

[traveler501]

Thanks for the extra info…I'll be careful with my choice of exhaust system mounts. Today was spent on a bunch of little things

that I want to get out of the way before doing the exhaust (which will likely involve driving the car to a shop). The motor has

a little over 500 miles on the rebuild and so I opened it up to check the valve lash and retorque the head and valve train. I was

pleasantly surprised at what I saw…some nice upgrades, and all shiny as clean. Tomorrow I'll do the oil change and then the

muffler is top of the list. Thanks again for all the helpful hints…here's a couple valve train pics. We all love pics, right? :drool:

 

cheers,

John

 

[Off Road SHO]

So I see a lot of excess silicone on the inside edge of that valve cover gasket. Make sure you remove all of that before you button it back up. Never good to have pieces of that non-disolvable rubber clogging up your oil pickup screen.

 

Nice and clean though, that's a good thing.

 

Tom

[Kitcat]

I have had Caterhams with both side and rear exhaust setups. Both were fume free, but my current side exhaust (wh/exits much further back than yours) is MUCH louder.

[TheDingo8MyBaby]

So I see a lot of excess silicone on the inside edge of that valve cover gasket. Make sure you remove all of that before you button it back up. Never good to have pieces of that non-disolvable rubber clogging up your oil pickup screen.

 

All I see is a rubber gasket that's been squished (likely from too much torque on the valve cover screws). I don't see any RTV.

 

Its hard to tell from the photos, but looks like you have dual valve springs. If you have a dial indicator, you may want to see how much valve lift you have to ensure you have the right valve clearances set.

 

Upgraded rocker posts and solid spacers are wise choices from the previous owner. I need to do them myself.

[traveler501]

Good questions….first of all, Tom gets points for a sharp eye…I did find two squishes of sealant and removed them. There are dual valve springs and in checking valve lift

I got approximately .430 on inlet and exhaust . The valves were originally set at .015 inlet and exhaust, I reset them to .012 in and .022 exhaust per the book but based

on the valve lift, that's very much in doubt! The PO is suggesting 15 in, 20 ex. Various grinds online range from 14/14 to 20/24 with that lift. Btw, it's supposed to be an

Isky Y-75E cam (although I can find no reference for that). I'll call Isky tomorrow.

 

Next day: Isky guys are away at a show, but I found out that Y-75E just refers to the date of manufacture (1975). I'll call them on Monday and see what else I can learn.

Sure glad you brought this up, Dingo!

Edited December 10, 2015 by traveler501