FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 2VNTG68S on October 28, 2017, 01:54:06 PM
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445 stroker built by Barry R. 495 Hp / 545 ft-lbs on Barry’s engine dyno
Best we could do on the chassis dyno was 365 Hp / 442 ft-lbs
I was shocked but the chassis tuner was not the least bit surprised.
Do those numbers indicate a breathing problem? Wondering if 2.5” exhaust was a huge compromise
Other factors:
Vintage Air
Power Steering
FPA headers
TKO 600
9” 3.70 Tru-Trac
Aluminum driveshaft.
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Not surprising considering all of the accessories and through the exhaust and driveline. Engine dyno measured at the flywheel. If you had the air cleaner on it, that is usually an easy 25hp hit.
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Doesn't surprise me. As Blair said, you're turning a lot of accessories, probably running an air cleaner, and turning a 9" rearend.
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Thanks guys - that’s helpful context.
I was considering going to 67 Shelby short nose hood (it’s a 68 Mustang vert) with a custom fiberglass air cleaner seal. Worth it to give it a straighter shot at the outside air?
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20% is what we usually allow so 23% is well within reason.
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20% is what we usually allow so 23% is well within reason.
I was hoping to be on the low end of that scale, lol
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I feel your pain, can be pretty humbling to put them on the rollers!! I think a lot is in the headers and exhaust that actually have to fit in the car, and of course the air filter can really be a bottleneck if hood clearance is an issue.
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Dyno headers vs real world headers for the vehicle can be a big factor. The density altitude in Barry's dyno room vs the chassis dyno room can account for a few percent either way too.
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I was considering going to 67 Shelby short nose hood (it’s a 68 Mustang vert) with a custom fiberglass air cleaner seal. Worth it to give it a straighter shot at the outside air?
I think a sealed outside air induction system is almost always a good idea and will help power. It might not help much on a chassis dyno though. The car isn't moving which defeats part of it's purpose. Was your hood open or closed when you were on the dyno?
paulie
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Was your hood open or closed when you were on the dyno?
It was closed but he had a huge floorstanding fan blowing at the Rad
I was thinking that since the HP impact was higher than the Torque impact it indicates a breathing restriction. My guess was the 2.5” exhaust.
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I was thinking that since the HP impact was higher than the Torque impact it indicates a breathing restriction. My guess was the 2.5” exhaust.
Considering you made 495 hp on the engine dyno, 3" exhaust can only help. It's entirely do-able in your Mustang chassis.
JMO,
paulie
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I was thinking that since the HP impact was higher than the Torque impact it indicates a breathing restriction. My guess was the 2.5” exhaust.
I see what you're saying, that at low rpm (torque peak) there was less difference, My feeling is that chassis dynos are so freakin' wonky in how they get their numbers, that I wouldn't put too much significance in the hp losing more percent than the torque, compared to the engine dyno. Engine dynos are usually much more accurate in what they are measuring. Still, if you can make some changes and improve your chassis dyno numbers, that's valuable.
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My 1975 F-250 4x4 with a 428/440 only has 295/327 on the rollers. It has a C6, 203 transfercase and 14 bolt rear. For some reason a n/a gasser looses more than a turbo diesel. My '01 Dodge 4x4 with a modified Cummins has 400/900. I used to tow with the FE but not anymore, lol.
Nick
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I bet the heat in the cramped mustang engine compartment steal a few horses to
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I bet the heat in the cramped mustang engine compartment steal a few horses to
this is the other reason I like the 67 Shelby hood - heat extractors.
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This thread just makes me want to buy a chasis dyno.....
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Yes, chassis dynos usually bring up more questions than they answer. I do think they have some value, but the numbers generated are far less accurate and far less precise than the numbers generated on engine dynos.
JMO,
paulie
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I know not everybody can or wants to run at a drag strip , but those numbers mean way more to me than any dyno sheet , be it engine or chassis , bragging papers I call them , Time slips don't lie , IMHO
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I agree. My focus has always been on street cars, where the real details are in how good it runs from idle to 4500rpms, so a dyno doesn't really mean as much.
I wish my local drag strip hadn't closed down (again). It was a lil 1/8 mile strip about 6 miles from my house. Made it nice to go off and mess around for a Friday evening. There is another track an hour away, but that prevents the spotaneous 8pm "hey lets go to the track"
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Agree , Ive tuned ( had to ) many big numbered dyno ( engine dyno ) that ran like crap on the street and at the track , the you don't drive a Dyno has more truth to it than is given credit :-) Dynos are great for trying and comparing different combos in an already proved combo , but outright not always the same
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I'm with you guys on the drag strip deal, (although i still ha vent got my latest combo on the track, getten close though) chassis dyno's are a good ball park tool i guess but it seems like the same car on 5 different dynos gets 5 different results. Especially those portable trailer mounted deals like the guy sometimes brings up to the truck stop on Saturday nights. At least i didn't have ta pay but who knows how far off that thing is and which way .
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If, and IF a dyno test is actually done with accuracy and everything is adjusted to get the best torque and horsepower reading, IT WILL prove itself on the track. It all comes down to the operators and if they maximized the combination on the dyno. That means every combination of headers, intakes, spacers, carburetors, timing, cam timing to get the best results and then repeatability. If all that is done properly, then the dyno sheet will be proven accurate at the strip. JMO, but I have done both the chassis dyno scene and the dyno scene on many engines over many years. Chassis dynos are just as susceptible to manipulation as an engine dyno. Joe-JDC
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My wifes uncle have a chassis dyno and do some high end
rally cars there im going to take the Galaxie there to tune
it.
What numbers i get in the end compared to another dyno
is not that interesting as i see it. Just to tune my combination
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I can't take my car on the strip unfortunately (convertible and I don't want to put in a roll bar). My ass-o-meter guess is that it would do low 12's. Even though the chassis dyno numbers were a surprise it pulls plenty hard.
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Well i hear the young guys with their turbo this and that talk about using a certain chassi dyno
beacuse it gives the highest numbers ::) yeahh right
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Chassis dyno numbers are only useful for comparison during tuning THAT car on THAT dyno. We'd probably be better off is they just gave us a number in percentages from one to one hundred based on pull comparisons.
I once took my car to one of those chassis dyno "contests" at a Car Craft show. At that time it would run between 10.40-10.80 depending on the track and weather. It laid down a solid 385HP on the dyno. Some guy with a 455 70 Grand Prix with a catalog cam and a set of headers made 400...car was three seconds slower in the 1/4...
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Chassis dyno numbers are only useful for comparison during tuning THAT car on THAT dyno. We'd probably be better off is they just gave us a number in percentages from one to one hundred based on pull comparisons.
I once took my car to one of those chassis dyno "contests" at a Car Craft show. At that time it would run between 10.40-10.80 depending on the track and weather. It laid down a solid 385HP on the dyno. Some guy with a 455 70 Grand Prix with a catalog cam and a set of headers made 400...car was three seconds slower in the 1/4...
Yes thats what im talking about i can tune it on that dyno what ever that numbers are. What nr another dyno shows is of no interest for me
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I agree. My focus has always been on street cars, where the real details are in how good it runs from idle to 4500rpms, so a dyno doesn't really mean as much.
I wish my local drag strip hadn't closed down (again). It was a lil 1/8 mile strip about 6 miles from my house. Made it nice to go off and mess around for a Friday evening. There is another track an hour away, but that prevents the spotaneous 8pm "hey lets go to the track"
What is the best way to assess/tune performance for the street? I was thinking a nice flat torque curve down to 2500 or so RPM was a good indicator, but even that would be run at WOT, so I'm not sure it indicates anything other than squeeling the tires at low RPM?
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Drive it.
Drive it everywhere, take the kids to boy scouts. Drive 50 miles in one direction and 50 miles back, try to improve fuel economy while not losing any power. Get it really stupidly hot racing around then sit at a redlight for 2 minutes. Go off into the country roads and tear them up and then pull into a gas station and park the car while the fuel boils and try to restart the engine.
Drive it 40 miles to the drag strip and get really horrible times because you have street tires and probably 500ft lbs of torque, then drive it home.
Let the car idle for 30 minutes as see how hot it gets on the hottest day.
Anytime a little issue pops up, fix it.
That's how I do it :P
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Drive it.
Drive it everywhere, take the kids to boy scouts. Drive 50 miles in one direction and 50 miles back, try to improve fuel economy while not losing any power. Get it really stupidly hot racing around then sit at a redlight for 2 minutes. Go off into the country roads and tear them up and then pull into a gas station and park the car while the fuel boils and try to restart the engine.
Drive it 40 miles to the drag strip and get really horrible times because you have street tires and probably 500ft lbs of torque, then drive it home.
Let the car idle for 30 minutes as see how hot it gets on the hottest day.
Anytime a little issue pops up, fix it.
That's how I do it :P
This is what I've been trying to do. The chassis dyno helped with most aspects of the tune but now I'm playing around with cold start, warm start, seeing how it responds to different cruising parameters etc... From my perspective the initial dyno tune at Barry's was a great baseline to make sure we were in the ballpark. The chassis tune got me closer with all the variables of exhaust, intake restrictions, etc... I feel that WOT is about as good as it will get. Now I feel I'm 90% there and just filling in around the edges.
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i guess a lot of it,on the chassis dyno and drag strip numbers has a lot to do with how well you have your car set up .i have a friend with a very mild engine in his drag car.he runs numbers that most people would need 100 more hp to match.he is one of those guys who can get everything out of what he has to work with.jmo, brian
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Do those numbers indicate a breathing problem? Wondering if 2.5” exhaust was a huge compromise
I recently put my 69 Mustang on a chassis dyno and lost 23% at the wheels as compared to a SuperFlow engine dyno. I had open headers on the engine dyno and full 3" Magnaflow exhaust on the chassis dyno. All I can say is that 2.5" exhaust will be more restrictive than 3" but it might not matter until an engine is over a certain HP. I have seen/heard many opinions on the benefit threshold from 2.5" to 3". Most say above 500hp. My personal thought is that your engine might put down a bit more HP with 3" but the installation hassle, drone, and extra decibels may not be worth it until 3" will provide a sizeable gain. By the way, my car is very LOUD even with full 3" exhaust. It would be quieter with 2.5"
Regarding drivetrain loss, I have automatic which probably doesn't help. Maybe it's no worse than the TKO600. Hard to know. I will always dyno the car at the same location so I can compare when I make changes. The place I went to mostly does Toyota's so an FE set on kill was a new experience for them. Ha!
I was on a new DynoJet 424xLC. Just curious what brand you were on?
-John
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In regard to noise, I put a full-length 3" stainless (321) exhaust system in my '63 Effie ICB/390-330, using Bassani 2 1/2 foot mufflers. I used '64 427 exhaust manifolds and went 3" from there back. Very Pleasant mellow tone.
KS
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I can offer this about under hood/outside air. Testing with a 500 HP 351C, underhood air regular 14" x 2" air cleaner vs tear drop hood, foam seal, 14x3" air cleaner - change was worth .3 and 3 MPH in the 1/8 on the drag strip. Huuuuuge.
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There's a reason most (all, that I know of) HP and performance calculators refer to, and use, crankshaft HP.
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i guess a lot of it,on the chassis dyno and drag strip numbers has a lot to do with how well you have your car set up .i have a friend with a very mild engine in his drag car.he runs numbers that most people would need 100 more hp to match.he is one of those guys who can get everything out of what he has to work with.jmo, brian
MPH vs weight is the best indicator. ET means nothing about power. ET changes with moon phase, sun spots, bad 60', day of the week, etc.
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ET changes with moon phase, sun spots, bad 60', day of the week, etc.
LOL! That certainly is true. My car has varied as much as 1.5 seconds as I've changed my style of launch, among other things. The 60' has varied by about as much, but the speed is always 114-115. It doesn't matter if I spin the first 60', killing the ET. You would think that a quicker launch and better 60' would mean that your trap speed would be higher since your car is getting a better 'start', but it just doesn't work that way.
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There are a lot of differences between manufactures of dyno's as well. My friend has two chassis dyno's and tells customers if you want bragging numbers get on the Dyno-Jet if you want real numbers get on the Mustang dyno. I hear some differences in engine dyno's. It's more about tuning than top power results.