Dyno'd my motor: HP sucks!

[dameeks]

I bought my FFR MKI about 3 months ago, used. The guy I bought it from told me most of the good stuff about the motor, and I've had no reason to doubt anything he told me. I wanted to take it to the dyno to know what it puts down now, so I have a reference point as I make mods to it. One thing I had noticed in the car is that it pulls great up to about 4K rpm in each gear, but then sort of leaves me wanting more power after 4k. So, here's what the motor has in it:

• 302 from a 1991 Mustang, EFI
• Motorsport b303 cam
• Heads: ported and polished, 2.02 valves (he said they came from a 1970 motor. Not sure what exactly)
• fully hydraulic and roller: rockers, etc.
• Cobra intake
• 72 mm intake tube
• 24 lb injectors
• forged pistons
• 9.8:1 compression
• underdrive pulleys

It also has the stock T5 tranny and 3.73 gears. I'm sure this isn't a complete enough picture of the motor to really tell what kind of power it should put out, but should give a good idea.

So, I go to the dyno, honestly not knowing what to expect. I've never owned a Cobra before, so knowing how quick it is makes me feel like it should be putting down 300 or so hp. Again, just a guess. Boy, was I wrong. Here's the dyno graph:



234 hp! That's all? The torque starts dropping off after about 4k, which is in line with how the car feels when driving it.

One thing that seems like a major constraint is the headers. I have the stock headers, feeding a j-pipe. The headers are small, and seem kinda crimped in a bunch of places. I don't have a great picture to show them, but here's one look at them:



Since the motor starts petering out at about 4k, maybe that's when the exhaust is really starting to be too much for the size/style of the headers, and starts limiting the power?

Does anyone have any thoughts on my motor and numbers? Do the numbers seem right for a fairly well built 302? Does my theory about the exhaust seem correct?

Any and all thoughts would be appreciated,

Darren

[snakeeyes]

Darren,

I'm no engine expert so I'll leave the input on that to the many people on this forum who know what they're talking about. I will say that your thoughts on the exhaust make sense.

I've owned a '90 5.0 Mustang for over 10 years now. I don't drive it much these days but I put almost 100K miles on it when it was my daily driver. You undoubtedly know this already but aside from bumping the timing and installing a K & N filter, the first thing everybody did when those cars were new was to change out the entire exhaust system. Those mods, plus steeper rear gears, were usually all that was needed to put an otherwise stock Mustang well into the 13's, so there's got to be something to the engine's perceived need for a less-restrictive exhaust.

Anyhow, I sympathize with you on the dyno issue. I know that every dyno is different, and you can get readings all over the map, etc., etc., but it still sucks when it shows less HP than you were expecting. My Mustang has all kinds of stuff added to it: a bigger throttle body, 1.6 roller rockers, bigger mass air meter, underdrive pulleys, nitrous, a Paxton blower, MAC long-tube headers, off-road H-pipe, Flowmasters, 3.55 gears, subframe connectors, etc.

At one point I bought one of those G-tech performance meters and made several passes with it. It was before I installed the Paxton or the nitrous, but after I had spent huge amounts of time making all of the other mods, and I was expecting to see HP numbers in the high-200's. Imagine my dismay when the best number I could generate was something like 195 HP! I was sure MY G-tech must have been off, so I borrowed another one from a friend, with similar results. I was pretty bummed, to say the least. In fact, I think I ordered the Paxton a few days later...the need for HP is a slippery slope.

Bob

[Edbo]

Assuming that's RWHP, it sounds about right to me. The OEM rating is about 225.
The OEM headers are always funky looking, they're tuned for torque.
Keep in mind this is a motor designed for a daily driver capable of 200K miles with little more than the occasional oil change.
You CAN have lots more HP, all it takes is money.

Ed

[dameeks]

Sorry, should have said, it is rwhp. I know the power game is a slippery slope, and I knew before I bought the car how it would play out. And, it's not just power, but the whole car: I want the original style Halibrand wheels, but I want 5 lug wheels. If I go 5 lug wheels, I'll want to change out the brakes to disks. If I'm going to do that, I'll have to mess with the axles, so why not just upgrade to IRS, etc., etc., etc.

So, without planning on throwing tons of cash at this thing, what is a reasonable amount of power that can be expected? And, what are the next logical things to upgrade? In case you can't tell, I'm not exactly an expert in this field. Yet. All in due time, I guess. I know there are other aspects to the motor that I haven't included here, but not sure how much they would add to the conversation. Let me know if there's something else that you feel would be good to know.

Darren

[HighPlainsDrifter]

Hi,
You have mismatch in your system somewhere.
My '87 put out 244 rwhp with only mufflers and ported stock heads,timing at 13*. @ 4,500 rpm.
That said, my '91 pulled hard to 5,300 rpm with the B303 cam so I think you have an over restricted exhaust, I would go to 1 5/8" shorty headers, 2 1/2" 'S' pipe and a better sidepipe, they can choke down 50 HP. Bump your static fuel pressure up to 42 PSI, timing to 12* with your compression, 180* thermostat, plugs set at .044 .
Good Luck,
Perry.

[blykins]

What brand dyno was it? Dynojets usually show about 15% more horsepower than Mustang brand dynomometers....

[Mr.Fixit]

Honestly, most people just estimate their engine's power and vastly overestimate it at that. HP is only a small part of what makes a car fast, so remember that the only piece of paper with numbers that matters comes from the racetrack, not the dyno shop. If you deside you really need more power, add up all the modifications you think you can't live without, it might be cheaper to buy a different cobra that is equipped more like your ideal than to buy all the parts and convert your cobra. just something to think about. You can still blow the doors off the hondas, right?

[dameeks]

blykins: it is a Dynojet, which based on your comment, doesn't make me feel any better.

Mr.Fixit: I know what you mean. I think every now and then that I should just sell it and get one totally decked out, but then I remember why I bought it to begin with. Which is, to have a new hobby. I've always wanted a Cobra, and really always wanted to build one. But, if I tried to build one myself it would take 5 years. So, this is a good middle ground. Something I can drive now, and can tinker with and upgrade to my heart's content.

HighPlainsDrifter: good info. I definitely think my problem is in exhaust flow. I'll start looking this weekend at the different options.

The last time I really worked on a hot rod was back in high school, on my 68 Camaro. You never heard about a car having a computer back then. So, if I want to check the timing, and possibly set it, where do I begin? Do they make some kind of handheld scanner that can tap into the computer? If so, what is the interface that is on a '91 motor? I've heard ODB1 and ODB2 thrown around a bit.

Thanks,
Darren

[blykins]

This engine isn't that new....if you want to check the timing, do it the old way....with a timing light....and to change it, just give the old distributor a twist.

[HighPlainsDrifter]

Darren,
To set the timing on a 5 L;

1st unplug the spout connector[black 1/2" shorting clip located about 10" from distributor in wiring]

Have engine warm and set timing normally. with your higher compression you need to make sure you have a 180 thermostat installed, not the 195* factory one.
Set timing at 12* BTDC
stop engine, put spout connecter back in.

Perry.

[jamvan]

Darren:

I agree with Ed, unless you start making significant changes to the engine, what you see is what you will get.

A 1991 Ford 302 while a great engine, was not known for making goobs of hp. OEM was about 235 HP provided it was properly tuned. In addition, the engine was designed to make maximun hp up to 4500 rpms.

I agree open the plugs up a little to .044 but only if you are using a MSD box. I guess you are at .030.

Good luck.

jim

[RICK LAKE]

dameeks Darren Those are good numbers for what you have in the motor. At 4 grand the valve spring may be going soft and not closing the valve as well. A b303 cam is small. This is a good motor for a cobra. You could put a backpressure gauge on your exhaust system and check for too much back pressure. 2 lbs is about perfect for the best of both worlds under WOT. Reliability is more important the the extra 5 hp you are looking for. What are you doing with the car?? Roadracing, Autocross, 1/4 mile, cruiser?? This is what you should build your motor for. Don't worry about HP, Build a tork motor good to 6000, You will be more than happy with what you have. I have a 452 that makes 358hp and 468 tork. 12.5 in the 1/4 mile and is very stretable. Something to think about. Tork makes it move, hp keeps it moving at high speed. Rick Lake

[Excaliber]

Better research the E-303 vs the B-303 cam.

ONE was for h.p. in the high rpm range with less torque, 5000-5500 and required better valve springs to make it work.

The OTHER one was a lower rpm torque type cam, 4200-4300 and it's done.

Regardless of what you might have been told it seems you DO have the torque cam. The stock FFR headers aren't that bad, they will easily support 5000 and higher rpm.

Figure about 280 or more flywheel horse. Not bad for what is essentially a "mildly" built 5.0.

The 24lb injectors were a nice call. Not to big and WAY better than the stock 19's (which are ORANGE). You can tell what size the injector by the color of it's top. Good A/F ratio throughout the pull so looking good there.

Mid 90's 5.0's ranged from 215, 225 and 235(?) horse. I think Ford measured the h.p. as NET (RWHP WITH ACCESSORIES).

215 was most common. They all came with roller cam. Port and polish stock head still won't equal what good after market alloy heads will do.

H.P. aint free anyway you look at it. The GREAT performance you got is a DIRECT RESULT of the Shelby formula for success. H.P. to weight ratio, thats EVERYTHING when it comes to performance.

[MJN]

Your dyno sheet looks about right for that motor. The Air/fuel ratio is pretty much spot on so don't go messing with fuel pressure. More timing will definitely help. With iron heads 12 -13 degrees base timing should be OK on 93 octane, with aluminum heads you can use a couple of degrees more. 2 or 3 degrees timing should pick up as much as 10ft lbs of torque and maybe 6 - 8HP.

Basically it looks like you have a well matched combination, if you change any one single thing you may not see much of a gain until you have changed everything. Going to 5/8" shotry headers may give you a few HP in the upper rpm's (5hp or so) but may lose you some bottom end torque. The FFR sidepipe and stock Mustang header set up can be replaced with a proper 4 into 4 for a larger gain in torque and HP. You should have a 65mm throttle body to work well with the Cobra intake and the mass air meter should be a minimum of 75mm, 80mm or larger would be better. That's about all you can do without getting inside the motor. You might see another 20HP with 4 into 4's , 65mm throttle body and larger MAF. If you want more HP with a HP to peak closer to 6000 rpm then consider a cam change but be prepared to lose that nice fat torque curve. To really wake up the motor at higher rpms a better flowing intake and probably better heads will be required along with a cam selected to work with them.

Building HP is an educational experience and education isn't cheap these days. Hey, it's only money, right? And besides that's part of the fun of owning one of these cars.

[Roscoe]

Not only do the bolt on parts have to 'match' each other, they have to be fine tuned to maximize your POTENTIAL. Many people bolt on parts and figure out their POTENTIAL horspower on paper. All are disappointed when they make their initial dyno run.

It takes more than just bolting on parts to make hp/torque.

As an example, read the dyno article I wrote for Kitcar Magazine

http://www.kitcarmag.com/techarticles/142_0401_dyno/

Roscoe

[Cracker]

Darren - your a victim of which dyno you used. In some cases around here you could be claiming you have a pump gas small block with 650 hp. At least you know where you really stand - enjoy it and don't worry about the #'s. You said it felt fast (or something like that) prior to the dyno so don't go hog wild - HP will cost you even with a small block.

[Roscoe]

Also remember the horsepower to weight ratio. You are driving a car that weighs in at around 2300. You don't need much to launch it.

Roscoe

[MidOHasp]

Darren...

Assuming drivetrain losses, you're making anywhere from 290-310 hp, probably a bigger range than that, not sure what kind of D/T losses you have. Does it sound cool? It's quick, right? So be happy with it! If you want a laminated dyno sheet that is bigger than mine, or his, or his over there, then open up the wallet. The motor will do more, to be sure!

I took my HP and TQ numbers down off my little avatar. I figure, who the heck cares. I built a 408 the way I wanted it and made over 500 horsepower. Yeah it runs on pump gas, but it runs a little better on Cam 2. I was hoping it would run best on pump. You'll read all about pump gas windsors making 8 gagillion horsepower, and it is not true. I figure if I can run a 12.0 1/4 mile, I'm not going to write it on my windshield when the Ford Excursion next to me that only has the 5.4 in it has "10.1" written in his windshield.

Why get into the "who has bigger balls" war when the guy next to me has a couple of baseballs crammed down the front of his pants.

No matter what you do, someone will always have more power than you. Someone will always be faster than you. And if you are the chosen one that has more power than everyone else and is faster than everyone else..... someone will always *claim* to be faster and more powerful than you.

I'd say pick your battles... and enjoy the crap out of your car. That's what they're for - not to be the fastest.


JP

[dameeks]

I appreciate all of the feedback. My goal with the car is a great street car, with the occasional trip to the drag strip, and hopefully, someday, some autocrossing. I don't have any desire to build a 700 hp monster, but I know I'd like more power in the top end. I guess I shouldn't act surprised at the numbers, given that they match pretty well with what I feel in the seat-of-the-pants. It was more just a shock, given that people do tend to state the highest possible number they think their motor could ever make. I guess that's what had me thinking that my motor would push a little more. I'm not upset, just wondering if the numbers are what you would expect, and where to go next to get a few more horsepower.

Roscoe, that kit car mag article was dead on. So much of it is in the tuning. At least now I have a real-world baseline, and I can always compare each mod I make to see how much power was really added.

I'm planning on going to the dragstrip tonight for the first time. Not being an expert driver, anyone wanna venture a guess on what it'll do? Tires are 275/50/15 BFG Radial TAs.

Darren

[MidOHasp]

I'm throwing a guess out there that you will run a 13.25 @ 115 mph.

With that kind of HP/TQ, use some judicious wheelspin.

If I'm within 1/2 second and 5 mph either way, do I win a prize?

JP

PS - enjoy.