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Ford 1999-up 4.6L SOHC engines vs restrictor plates


TurboShortBus

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I'm not sure if anybody is running a 1999-up 4.6L SOHC engine (aka PI) in their CMC car, but if you are, is it necessary to run a restrictor plate to keep the power in the 230-237 range to the tires? They are rated at 260 hp, and guessing at 15% driveline loss, that's about 221 to the tires. Free up the exhaust (off road pipe, etc.) and ditch a few other parts to gain 20 hp at the crank, and you can probably find yourself past that 237 rwhp limit. Especially, in another post, if it's easy to take a 225 crank hp Fox Mustang and make 230 to the tires by ditching parts and freeing up some power.

 

Mark

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Tony G, Charles Weeks and myself run that motor and we run restrictors. Unrestricted we are all in the 24x-25x range. This thread shows the restrictors 50 and 45mm.

 

http://www.camaromustangchallenge.com/forum/viewtopic.php?t=2317&highlight=

 

I'm 252/292 unrestricted, stock motor with open exhaust and pulleys.

The 50mm restrictor puts down 244/282.

The 45mm restrictor puts down 229/269.

 

The tq really takes a killing with the 45mm. I've heard the LT1's don't loose much tq when they choke them down but the SOHC doesn't like it for TQ.

 

OT: I had 3.27 gears the first two years then went to to 3.73 and the dyno's were identical for both sets of gears. I also think 4.1 may not be a bad choice with the extra RPM's the SOHC motor gives you.

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by ditching parts and freeing up some power.

 

Not much to really do to the SOHC other than off road x or h pipe, pulleys and remove the A/C. My EGR and all other emissions system is still in tact except for the fuel canister vent line that runs to the back of the manifold. Mine broke during our three hour enduro a couple of years ago and I capped off the mainfold, removed the canister by the fuel tank and put a breather on that line and it's never had any issues. Same HP/TQ with or without that vent line. Oh, and remove your check engine light bulb from the cluster

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Oh, and remove your check engine light bulb from the cluster

 

Definitely! Actually, my buddy's shop has all of the SCT software, so he can shut off all of those pesky little lights and codes for emissions, EGR, PATS, and whatnot.

 

Mark

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Oh, and remove your check engine light bulb from the cluster

 

Definitely! Actually, my buddy's shop has all of the SCT software, so he can shut off all of those pesky little lights and codes for emissions, EGR, PATS, and whatnot.

 

Mark

not legal for CMC.

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not legal for CMC.

 

So, it's illegal to only turn off error codes and the anti-theft system? Per the letter of the law, I suppose it is, but I'll argue all day long that it's not a performance advantage, especially when it allows me to start the car without having the original $85 key (PATS system). It won't matter for my upcoming year or so of HPDE, anyway. I'll cross that bridge when I get to it.

 

Mark

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not legal for CMC.

 

So, it's illegal to only turn off error codes and the anti-theft system? Per the letter of the law, I suppose it is, but I'll argue all day long that it's not a performance advantage, especially when it allows me to start the car without having the original $85 key (PATS system). It won't matter for my upcoming year or so of HPDE, anyway. I'll cross that bridge when I get to it.

 

Mark

dont think for a minute that your the only one who has felt this way when they came to the series. i too think its BS w/ regards to emissions stuff. but the fact its, its not legal. get a stock tune put ina deal w/ the engine light like the rest of us EFI guys.

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dont think for a minute that your the only one who has felt this way when they came to the series. i too think its BS w/ regards to emissions stuff. but the fact its, its not legal. get a stock tune put ina deal w/ the engine light like the rest of us EFI guys.

 

Ah, gotcha. Don't get me wrong, I appreciate the efforts of the CMC series to keep everything as inexpensive as possible, and to keep sneaky electronic shenanigans to a minimum. But, any time there's a computer involved, there is always the possibility of somebody getting sneaky on an undetectable level, so it's basically "honor among thieves."

 

Besides, downloading a performance program into the ECU of a 252 rwhp car while running an intake restrictor to get it down to 230 rwhp just doesn't make a lot of sense...lol. Maybe the thought is that we shouldn't be able to spend megasoftwarebucks to tune our way "down" to 230 rwhp while being able to adjust several parameters to try to get the torque up closer to 300, which is presumably why the Fords get a 50 lb weight break in Tables 2 and 3.

 

Mark

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dont use the "honor among thieves" w/ regards to the EFI guys. reflashing a PCM is much more involved than a jet change on a carb. or a twist of the distributor between rounds. its just as easy for ANYONE to cheat as it is for the EFI guys.

i'm on your side as far as "i wish i could". it would be nice to know that if the light is on, there is a real problem w/ the car.

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I've heard the LT1's don't loose much tq when they choke them down but the SOHC doesn't like it for TQ.

 

Only till you get to 3500 rpm, then it begins dropping like a rock.

 

I suspect that is true for any restricted motor, though. You restrict air, you kill the big end power.

 

One thing I've noticed is that my car runs grossly rich with the restrictor plate. Anyone else seeing this with restricted motors?

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This may just be the stupid coming out, but has anybody tried restricting the exhaust instead of the intake? There's the whole theory of "the engine likes some backpressure" for bottom-end power that may or may not be true. Granted, it's much easier to just machine a spacer and slap it on the throttle body inlet instead of jacking up the car, getting under it, messing with hot parts and welders, etc. I'm considering leaving the cats intact, ditching the stock after-cat exhaust (which is rusted out), and just attaching some 45* tubes to the back of the H-pipe and turning them out the sides in front of the rear tires, 2000 Cobra R style.

 

Just a thought...

 

Mark

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7.7.2 2nd paragraph.

Cars may install a restrictor plate between the air filter and intake manifold to reduce horsepower and torque.

 

Damn rule book is at home on my coffee table, Adobe reader is questionable on this computer, and I'm on a jobsite watching skid-steers run into things...lol

 

But, did anybody ever try leaving the cats on, and maybe only running dual 2.25" mufflers (instead of off-road pipes and 2.5" free-flowing exhaust), and seeing where that puts the hp/tq numbers? That's much cheaper than a $150 off-road pipe and $150 for a pair of Flowbastids with turn-downs and flow tubes. The extra weight of the cats could help to get a gutted car back to 3150 lbs (in the case of a Mustang), instead of buying 150 lbs worth of ballast (although the passenger's seat is further back than the cats are), and we could be somewhat "green" in the process (what in the hell is wrong with me? I even consciously put cats on my last project car, in a state with no emissions or vehicle inspections).

 

Mark

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". it would be nice to know that if the light is on, there is a real problem w/ the car.

 

I scan it a couple of times per race weekend to make sure I don't have anything unusual. I get the code for no cat's and the fuel canister constantly so I just took the light out.

 

7.7.2 2nd paragraph.

Cars may install a restrictor plate between the air filter and intake manifold to reduce horsepower and torque.

 

But, did anybody ever try leaving the cats on, and maybe only running dual 2.25" mufflers (instead of off-road pipes and 2.5" free-flowing exhaust), and seeing where that puts the hp/tq numbers? That's much cheaper than a $150 off-road pipe and $150 for a pair of Flowbastids with turn-downs and flow tubes. The extra weight of the cats could help to get a gutted car back to 3150 lbs (in the case of a Mustang), instead of buying 150 lbs worth of ballast (although the passenger's seat is further back than the cats are), and we could be somewhat "green" in the process (what in the hell is wrong with me? I even consciously put cats on my last project car, in a state with no emissions or vehicle inspections).

 

Mark

 

8.26. Exhaust

All cars must use OEM stock exhaust manifolds. Any suitable exhaust system may be used after the OEM stock exhaust manifolds.

So if a smaller exhaust or single exhaust happens to reduce power, so be it. It's still "suitable".

 

Cat removal on my car gained 15hp and 15 tq at the wheels.

 

I had the following exhaust mods with no change in HP or TQ

- muffs with dumps (too quiet )

- straight dumps (too loud )

- full exhaust out the rear with straight pipes in place of the muffs (quieter inside, still loud outside)

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Kevin...if you were at 252/292 with open exhaust, pulleys, and no restrictor plate, then putting the cats back on theoretically brings you down to 237/277. Stock pulleys would probably kill another few ponies, winding up right around your current 229/269 with your 45mm restrictor. But, sticking with the stock stuff is a lot cheaper (aka "free") than buying off road pipes, mufflers, and billet restrictors. Of course, there's always the issue of *where* that 229/269 happens on the dyno curve. If the aftermarket parts manage to shift those curves to more favorable locations, then they are worth it. Also, I wonder if cats will hold up to racing conditions before failing or falling apart.

 

I'm basically cheap, that's all.

 

Mark

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I think the LT1 cars are pretty much in the same boat as you describe Kev: torque gets hammered unless you specifically plan for it. It very well may be the best answer is to leave some of the stuff these cars came with and have to restrict less. I didnt have that option since mine came as a race car but I've never seen tq over 280 on any of my dynos.

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I'll be the guinea pig for the "leave the stock junk on and see what happens" scenario, once I get a running 4.6L 2V swapped into this blown up 2002 GT in my driveway. I'm hoping that I can get the engine swapped out this weekend, if I'm lucky.

 

Mark

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  • 2 weeks later...

OK, I just picked up a mostly stock, 31k-mile 2004 Mustang GT today. 5-speed with Flowbastid mufflers, stock tailpipes, stock cats, and maybe a K&N filter. I'll slap this thing on the dyno in the next few weeks to see what it can do, and I'll find out what it takes to get it right at 230 to the tires while spending as little as possible.

 

Mark

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OK, I just picked up a mostly stock, 31k-mile 2004 Mustang GT today. 5-speed with Flowbastid mufflers, stock tailpipes, stock cats, and maybe a K&N filter. I'll slap this thing on the dyno in the next few weeks to see what it can do, and I'll find out what it takes to get it right at 230 to the tires while spending as little as possible.

 

Mark

 

You will see 224-226 with that setup. That is my bet.

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You will see 224-226 with that setup. That is my bet.

 

I won't argue with that! That's right in the ballpark with my guess. But, if that's the number that it makes, then there's no need for off-road pipes, underdrive pulleys, cold air kits, and then a restrictor plate!

 

Mark

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You will see 224-226 with that setup. That is my bet.

 

I won't argue with that! That's right in the ballpark with my guess. But, if that's the number that it makes, then there's no need for off-road pipes, underdrive pulleys, cold air kits, and then a restrictor plate!

 

Mark

 

IMO, the cold air kits don't do much if anything. The stock inlet tube is rubber and doesn't transfer heat like a metal tube. I've dyno'd mustangs and a 2000 lightning with open type K&N filters and both lost hp/tq on the dyno over the stock air boxes with the snorkel removed. Stock setup is free and works GREAT!

Steeda pulleys for the SOHC are really nice and include a SFI balancer which should enhance engine longevity. Hard to beat for about $200 and I did notice a smoother running engine in the higher RPMs with the balancer and it helps reduce/eliminate water pump cavitation.

 

You'll be in the 230s easily.

 

You'll find these motors don't need much work if any at all. I replace the plugs and change the oil. Oh, and one starter in three years.

Nothing fancy, keep it simple.

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One more money saving thing, your stock radiator will keep you cool on the track. I used a 180 deg thermostat and it never got over 210 on the hottest of days. After a rock put a small hole in my stock one, I put in a fluidyne but the stock unit works fine.

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One more money saving thing, your stock radiator will keep you cool on the track. I used a 180 deg thermostat and it never got over 210 on the hottest of days. After a rock put a small hole in my stock one, I put in a fluidyne but the stock unit works fine.

 

Thanks, that's VERY good to know! I suspect that the stock AC condenser will protect the stock radiator from shrapnel, but I'll eventually be removing it.

 

Mark

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  • 1 year later...
OK, I just picked up a mostly stock, 31k-mile 2004 Mustang GT today. 5-speed with Flowbastid mufflers, stock tailpipes, stock cats, and maybe a K&N filter. I'll slap this thing on the dyno in the next few weeks to see what it can do, and I'll find out what it takes to get it right at 230 to the tires while spending as little as possible.

 

Mark

 

You will see 224-226 with that setup. That is my bet.

Update, a year and a half later...

 

The car made 235 rwhp a while back (NASA dyno procedures were followed). The only non-OEM power parts were the Flowbastid mufflers welded into the stock tailpipes. I even reused an old, dirty paper filter from another car. Cats, EGR, etc. are all original and fully intact.

 

A K&N filter (it came with the car) was worth precisely 0.1 rwhp. It's going on eBay.

 

A Superchips tuner (it came with the car) was worth 2.6 rwhp and 3.5 rwtq at peak, but approximately 7 rwtq at the biggest gap on the graph. It's heading for eBay as well.

 

Mark

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