FBIII

How much "extra hp" would it take to get an OB to 170mph?

heinrich

Jim I remember from Excellence Was Expected that it was 6-litres. Anyway memory fades. FBI, that is one of the best questions i've ever heard asked.

AO

I don't think it was all HP dependent. I think a lot of it was also drag limited (but this is a guess on my part). The reason for my thinking is the 80-83 Euros with 300 HP were said to have a top speed of about 155MPH vs. the 77-79 Euro with 230 HP that had a reported top speed of 143MPH.

I'll bet dollars to donuts that the 80-83 Euro got to top speed much faster than the 77-79.

I know gearing also plays a big part on the top speed determination, and honestly I have not researched (no desire to). So that could have also been a determining factor. Could be these cars were geared to that top speed.

Anyone know for sure?

FBIII

Andy, That's what I was inferring. I think the big hurdle is the higher coefficent of friction and maybe to a lesser extent lower torque. I was doing a search for an appropriate physics equation but wasn't able to find one very easily.

m21sniper

No idea, but i've had mine well over 150mph(if my speedo is to believed).

There is a formula to determine top speeds, but i don't know it off the top of my head. I'm sure mr. google does though...

IcemanG17

The original non-S cars did tend to get light in the front at high speeds...which is why the S spoilers came out...which led to the S4 and so on..... If I remember correctly the S and original body both had a drag number of about .39 vs .34-.35 for S4-GTS....so an OB with the same HP as a Euro S or USA S3 should go about the same speed (assuming same gearing-trans etc)...if 288-310 hp will push it to 155-160 then how much more is needed to reach 170? You got me on that one...but the ORR guys will know

m21sniper

If i'm not mistaken once you hit a certain critical speed it requires an exponential increase in HP for additonal mph. That might be for ships though, lol....it's been a while.

EDIT TO ADD: Here's a formula for determining max vehicle top speed:
http://www.perfectracing.com/techtip...tspeedcalc.htm

tv

Just from memory from what i have read here and what i have seen on the tube. Sniper is right about the horsepower needed for more speed at very high velocity. On a tv show they once said it was 7 hp for each additional mph and that was i think aroung 180 or so.

Also in a long thread here about a year or so ago, it was thought that the ob (euro) with higher gearing would max out better (toward redline) than an S4 with the higher gearing 2.2 because it would be drag limited. The gearing would make better use of available power against the wind.

Has anyone redlined a euro S2 in auto or manual in top gear? (i remember one of the brit members talking about a long trip in europe at 160+ on speedo) What is the highest rpm's achieved on road in an S4 in top gear? I have heard numerous times of S4's maxing out dynos at 200mph +.

hacker-pschorr

Update - I spoke to Todd last night, he is hoping to have this engine installed / running by this weekend.

F451

Videos please...

Barry Johnson

Holy crap, thats awesome... Someone asked if the S4 would flow enough for that bore, and IIRC, an S4 head can't hold valves large enough for really much above 6l. I'm sure Sensei Louie would know :^)

slate blue

Hacker is it a two or four valve engine? Sorry if I missed that.

Cheers Greg

hacker-pschorr

Greg - 87 S4 - 32 Valve

tammons

And the drive train to handle that beast ??

tv

That is going to sound AMAZING! The pictures in that link in the old thread are really something, A/N fittings on flexible hose, trans case empty then filled, headers and huge exhaust. It would be nice to know how the sleeves were secured in the block.

It would be really nice to see/hear video of this monster starting up and idling. The sleeves are made of what??