Dyno tune

[exfed12825]

Took my MGB to have it dyno tuned. It hit 374.8 hp and 341 ft lbs at 6600 RPM on the ground. The tuner said I ran out of air at that point. He also did a 1/4 mile pull which came out at 9.8 seconds @ 146 mph. I know the engine is capable of more but I'm satisfied with that for now, I'm going to check into a larger throttle body and bigger injectors, maybe a cam. It did hold those numbers past 7200 rpm but wasn't gaining anything. The dyno was inside a garage and he didn't have a blower to push air past the throttle body which would have helped sort of like the hood scoop does.

[rficalora]

Those are some pretty impressive numbers Tony!  I have way less and still spin the tires before using all of it; have you done anything to help get the power to the ground?

[RMO 699F]

Those are very impressive #'s Tony, congratulations! Although I must say sub ten second mgbs are far and few between..chuckle...look forward to seeing you in Townsend in October!

[exfed12825]

This MGB is equipped  with computer controlled traction control which retards the timing if it senses wheel spin. The Fast XFI 2.0 computer controls fuel, air, ignition timing, and traction. I called the engine builder today and discussed the dyno results and he was pretty surprised at the low numbers on HP, torque, and RPM's. He said that similar engines he has built were putting down 450 plus HP and over 400 ft/lbs at 7200 RPM's. He suggested a different tuner with more knowledge of the Fast 2.0 computer system. You do understand that the 1/4 mile pull was on the dyno and under track conditions would be quite different, especially considering that my drag racing style is that of an very, very, very, old man

[BlownMGB-V8]

Bear in mind, the headers on an MGB are usually no help in making horsepower.

Jim

[RMO 699F]

Tony, I get it on the quarter mile thing...nowdays, as soon as I see a light, any light....I am dumping the clutch...and I'm still way tardy on the reaction time...smile....

[MGBV8]

:-)

[exfed12825]

The last time I went drag racing, 18 years ago, the best light I could pull was a point eight ,  My wife and kids were standing on the wall yelling at me to go and laughing their butts off.

[HealeyRick]

Tony,

Impressive numbers.  Looking at your avatar info, this motor turned 530 hp at the crank?  So you lost almost 160 hp between the crank and wheels?  About 30% parasitic loss.  Reason I ask is I went from 345 at the crank to 199 at the wheels and am trying to figure out where the power went.  Only thing I can think of is the Sunbeam Tiger log manifolds I'm using and my next project will be some headers.

[tbo]

Just wondering  how old do you have to be to be very very very old. ?

[weinerdog500]

hey, i'd like to see some. pics of your v8 B!. ..Also Rick F, what gearbox, rear are you using? and tires, size? Do you lose traction beyond 1st?

[MGBV8]

Rob F. ?  Here's is his car.

http://www.britishv8.org/MG/RobFicalora.htm

And many others.

http://www.britishv8.org/Photos-MG-Conversions.htm

[rficalora]

Lonnie - When I had Falken ZIEX ZE-912's I could sprint the tires in the first two gears easily and in third under hard acceleration.  I now have BFG Rivals (still 225 width but 225/45 vs the 225/50 falkens I had).  I can accelerate a LOT harder, but can still spin the tires in 1st and break loose in 2nd too.  Haven't broken loose in 3rd with the Rivals.

Trans/rear gear info is at the link Carl posted.  May change to a regular mustang T5 and maybe rear gear someday, but having too much fun driving it for now!

[Jim Stabe]

Restrictive exhaust can really affect the power you get in the real world. I run 1 5/8" block hugger headers into dual 2 1/2" pipes merging into a single 3" pipe leading to a 3" muffler in the back. With the original can it made 543 rwtq at 4000 rpm and 450 rwhp at 4800 rpm. I was puzzled by the low rpm peak for the HP and was advised to get rid of the 50 series Flowmaster muffler I was using and put on a Dynomax straight through instead. I did replace the muffler but committed the mortal sin of making a cam change at the same time because I didn't want to pay for the extra dyno run. I changed the cam because the car would start to catch in 6th gear if I went much below 70 mph on the freeway, above 70 it was fine (1700 rpm being the dividing line). The cam I replaced it with had 10 degrees less duration and a wider LSA so you would expect it to produce a little less peak HP and do it at a slightly lower rpm. The results however, were 465 rwhp at 5750 rpm and 479 rwtq at 4000 rpm. Without separate tests I can only surmise that the exhaust restriction was choking off the old cam above 4500 rpm since the new, milder cam peaked 1000 rpm higher in the range. If I extrapolated the HP curve of the old cam to peak at 5800 rpm, it would have made around 500 rwhp. Even with the lower HP I'm much happier driving the car now and it still has more than enough power for me.

My point is, the street exhaust can really strangle an engine compared to a set of engine dyno headers. The chart below is an interesting comparison of muffler flow rates.

[HealeyRick]

Thanks for that post, Jim.  There were only two changes made to my motor from the engine dyno to the chassis dyno... air cleaner and exhaust.  I can see losing a bit on the air cleaner, I'm using the HiPo 289 one.  I suspected most of the drop, though, is due to the cast manifolds, but now you've given me something else to think about since I have Spintech mufflers, too.  They don't do very well in your chart, which is quite surprising.  Probably not much choice there, though as they're about the only thing that will fit under the car.

[Jim Stabe]

I was out of room on my car for a muffler also so I built a "house" in the trunk just ahead of the license plate. It is about 4" tall and long enough to accept a 21" long oval muffler. I put heat insulation on the underside to keep heat out of the trunk. 3" tubing goes under the driveshaft and around the gas tank on the passenger side and the outlet is in the stock MGB location - probably not fooling anyone.

[BlownMGB-V8]

After all of that and you have no trunk?

Jim

[Jim Stabe]

Actually, there is quite a bit of room in the trunk. There is a space above the rear end that would take a small suitcase and plenty of room for a set of golf clubs if I played golf. The car wasn't built to travel in but I could easily fit in everything needed for a weekend trip, even my wife's "essentials". I only lost about 4" for the muffler but gained a full 11" of width.

[Dan B]

Jim S....are the numbers for the 3" comparable to the 2.5" on the chart?

[Jim Stabe]

The 3" versions weren't tested but the construction is the same so I assume the results would be comparable. I think the Flowmaster has the exact same internals for all of the 50 series and the only thing that changes are the inlet and outlet pipe sizes. The Dynomax I have has a 3" straight through core so I imagine they change the core to match the inlet and outlet size. The difference in sound was significant. The Flowmaster was louder and it had an awful resonance between 1800 and 2400 rpm, which is exactly where it wants to run on the freeway. The Dynomax was actually quieter despite the 3" straight through core and it has no resonance. I also like the tone better with the Dynomax.

I have a 3" Flowmaster 50 series for sale that only has a couple hundred miles and a few dyno pulls - just in case anyone is interested.

[roverman]

Jin, Will it fit a Fiero ?  The 2.8L has too much power for me.....

[Jim Stabe]

Art

You can make anything fit.

[MGBV8]

What did Art just say?!

I have a 3" Flowmaster 50 series for sale that only has a couple hundred miles and a few dyno pulls - just in case anyone is interested.

I have 2 of 'em on my '68 Camaro.  They sound horrible.  Give me back my Cherry Bomb header mufflers!