Considering Coyote build with cross-flow under car exhaust system.

[Mattnshilp]

I am considering buidling a BDR with a Coyote. But my U.S. NJ state requirements for a modern engine essentially require me to build the car with a standard under car exhaust with mufflers.

Since I know you guys are restricted and seam to build most of your cars this way, I thought you would be a good resource...

I need an OBD-2 port and exhaust sensor to pass my state inspections. I am considering a Coyote engine with OBD-2 port, cross-flow under car exhaust system with mufflers.

Is there a certain exhaust system that works well with the Cobra. I am concerned about ground clearance and was considering oval piping and narrow mufflers and such.

Any suggestions, opinions and experience would be appreciated.

-Matt

[Aussie Mike]

Are you talking about full crossover headers like a GT40 runs or just headers with an X-Pipe? Full crossover headers will be near impossible but you should be able to run some under body headers and an X-pipe easy enough. There's a lot of guys down here in Australia running underbody exhaust systems, mainly because side pipes are illegal in most states.

One advantage you do have with the Coyote motor is that the exhaust ports point more downward than a windsor and you don't need to make clearance for plugs. this makes building headers a much easier proposition.

Cheers

[Mattnshilp]

Originally Posted by Aussie Mike

Are you talking about full crossover headers like a GT40 runs or just headers with an X-Pipe? Full crossover headers will be near impossible but you should be able to run some under body headers and an X-pipe easy enough. There's a lot of guys down here in Australia running underbody exhaust systems, mainly because side pipes are illegal in most states.

One advantage you do have with the Coyote motor is that the exhaust ports point more downward than a windsor and you don't need to make clearance for plugs. this makes building headers a much easier proposition.

Cheers

I'm walking new ground with this idea. I initially planned on a Ford racing 427 and side pipes. So the Coyote is a different idea, but one I think I will be happy with in the long run. I'm not looking to re-invent the wheel, or try something crazy. I want to put together a good car using well established systems.

So, Mike, how would you do the exhaust with this engine if it where your car and you had the restrictions we both seam to have? Is there a certain cross pipe system that works and fits well with the Cobra considering the ground clearance issues and such? A muffler needs to be in the equation.

[letsboogie351]

Matt
A lot will depend on the chasis itself and what room is available for mufflers. A good exhaust fitter will be able to guide you with this. As Mike said many here in Australia run under car systems. With the cats and mufflers under my cobra I have about 105 mm of ground clearance.
Ps you are making me jealous already with the Coyote motor. I have the 5.4 Quad cam engine and truly enjoy the fuel injection.

Doug

[Modena]

Matt, your questions seem to me to be looking an off-the-shelf solution - sadly there isn't one, and you (or the exhaust shop) will have to build the exhaust, and probably build the headers too as I doubt there would be off the shelf headers available to suit a Coyote/Cobra combination yet.

[Cashburn]

We've done under car exhaust, but you cannot get a crossover in there. We also have factory side pipes with cats now.

[Jerry Clayton]

why do you need a cross over???and yes I know about what they add to a system and there are several ways to do it, some more helpful than others.

If it is a NJ state requirement, a good place to do one for compliance could be under the differential since it doesn't move and wouldn't need a lot of clearance.

You also could maybe just cross the pipes from 2 cylinders under the oil pan area and run the others straight back ( or even into side pipes((with cats))

[Mattnshilp]

I don't need a crossover. But if it was possible...

Sounds like it's not.

Thanks everyone.

I would still imagine I would give the engine more breathing room and keep my HP with an undercar exhaust system as compared to sidepipes with cats. No?

[Jerry Clayton]

Well---if you don't need it???????

The use of a cross over or x pipe on RACE cars came about because the cylinders don't fire evenly on either side and adding a crossover allowed some of that extra exhause to exit down the other side piping--IE--from the x on back they shared the muffler/tailpipe---

The odds of you ever being able to utilize the extra power from an crossover exhaust in one of these cars is very mimimable and I would have to advise you not to let this stand in your way---

However, if NJ has some specific rules about exhaust, you need to get a copy of their exact wording, examine there intent and work around that. If they don't have specific demands about the exhaust, then you don't need to be concerned if you want one of these cars.

[Mattnshilp]

The cross-flow was for performance only. The cats, obd2 and muffler are for the state.

Based on Cashburn's feedback, crossing pipes is not even an option. So it's a non-issue. Especially since he will be building the car for me.

So my last question then becomes-

Would a normal non-crossed undercar exhaust with cats and a muffler still give more airflow and HP then sidepipes with cats?

[Jerry Clayton]

Side pipes will be the most HP--with or without the cats, an undercar system won't come close to what you can do with sidepipes--

However---it is a fact that a lot of sidepipes out there are very restrictive and cost a lot of power---you have to make a wise choice

[Aussie Mike]

You can run side pipes with cats and O2 sensors. I've built several sets so far and they work fine.

They have to be a bit fatter to fit the cats inside. I make the body from 4.5" tube and the cat is 4" OD + a bit for the welds on the ends of the cat body.

The O2 sensor is in the collector just before the cat and is nearly invisible from outside the car. You have to crawl underneath to see them.




Food for thought.

Cheers

[YerDugliness]

Aussie Mike, I like your idea!

I have no issues with ECU's in a Cobra. Our states all have different requirements regarding smog abatement on cars and there's nothing in the law designed to ensure reciprocity between states. I live in a huge state in the U.S. and many of the more populous counties have more restrictive requirements regarding emissions than others. The lesser populated counties don't have to endure "sniffer" tests (now done through the ECU), whereas the more sparsely populated states require safety inspections only. It's a mess, and the utilization of an ECU with cats and O2 sensors would make it SO much easier to move from county to county within my state, much less from state to state in the union.

.....and that doesn't even begin to take into account the improved drivability of a car with an ECU, the ability to maintain a correct air:fuel ratio when gaining altitude, and so on and so on and so on.

Sadly, my Cobra has only a carb and a distributor, but when I switch the engine out for a 351C, I'm considering adding an ECU to the mix. It's good for drivability (I'll be located close to sea level for a while, then will be moving close to the Rocky Mountains soon, the foothills of which are at 5,200 feet), it's good for emissions, it's good for fuel economy, it's tunable....hard to find a downside to ECU's, IMHO.

Cheers!! from Dugly

[Jac Mac]

Some food for thought:
1. If you do a crossover setup [ 180° as per GT40 ] on a Cobra remember much of the GT40 sound is due to the two tailpipes being close together, In the Cobra instance if thay are some distance apart each tailpipe will sound like a single 4cyl exhaust, perhaps not what your after.

2. I built a system for a SBF powered TVR that races out here in NZ, each bank of headers go into a 'flat' collector as per any normal V8 setup & then the tailpipes from each collector go into one large flowmaster type muffler [ dual inlet/single outlet - self built ] and then one large oval tailpipe exiting out the rear, so its effectively an 8 into 1.... The exhaust note on this thing sounds quite 'sophisticated' for want of a better term & has an absolutely delicious howl once it reachs ~ 4/5000RPM, yet complies with the 95db limit on the tracks we race it at. There were several Cobras @ the Hampton Downs meeting in NZ earlier this year & all of those guys were very interested as to whether a system like this could be fitted to their own cars.

3. I have built several similar systems for road cars now, incl one 351c Tunnel Rammed Ford Falcon, on a quiet sunday or saturday afternoon I can pick the exhaust note of that car anywhere in town & the owner just loves getting it up in the RPM range where it starts to boogie sound wise.