Countach, the ultimate supercar

The Mimran Downdraft has Raymond's MSD box, although we have the original MM box and a spare NOS MM box on the shelf.

We used Raymond's box for two reasons:

Firstly, it is superior to the MM box.

Secondly, we felt it was a nod of respect to the man who developed it for himself & others and used it on this car.

I have no idea what output gear set is in there, but the trans works beautifully and the car accelerates like no other Countach I've sat in, including a pair of 25ths I owned in the past.

Correct.

That is awesome, I'll post it over in the Downdraft thread if you don't mind.

Changing the headers & exhaust alone will not make a real difference in overall performance in terms of acceleration & top speed. The Bosch FI itself imposes a limit on the engine’s breathing. The reason for this is that to meet USA EPA mandates, the air metering system is an engineered mechanical application that requires relatively smooth airflow, so, this explains why the cams of an FI Countach have a mild profile. Thus, even if you change change out the headers to free-flow items and apply a sport exhaust on a Fuelie, that alone won't really change the performance, but it will sound better and be more responsive. Bear in mind much of the superior performance of the Downdraft comes from the engine's heart with higher-compression pistons and more aggressive cam-profiles, carburetors notwithstanding. That's why some Downdrafts with boxed mufflers still did well over 180 mph. Also, if you start messing with a USA Fuelie and modify the cams for more aggressive profiles (for example), then the Bosch CIS will not run properly.

 

It might be worth noting that in order to be able to have an intelligent discussion on the QV engines (Carb or Fuelie) I went directly to the source and I reached out to the Chief Engineer who was responsible for them at the Lamborghini factory, Ing. Luigi Marmirolli himself.

He graciously shared many never-before-published details, including http://www.ferrarichat.com/forum/144273801-post8.html , http://www.ferrarichat.com/forum/144273804-post9.html , and kindly afforded this interview http://www.ferrarichat.com/forum/144273809-post10.html

As already discussed, the assertions that the 2 engine variants (Carb & Fuelie) possess the same basic potency is erroneous, and the fact remains that the Downdraft engine (Motore Tipo L 507 V4 fitted with the 6 Weber 44 DCNF vertical twin-barrel carburettors) is more powerful because it uses higher-compression pistons and more aggressive camshafts.

I have not seen the cam profile, and I don’t need to, because the Chief Engineer himself has affirmed that the Fuelie cam profile is milder and the Downdraft’s are more aggressively lobed (in fact Dani T compared them side-by-side and reached the same conclusion). To support this assertion, the camshafts, they are completely different part numbers, those used in the Downdraft are part numbers, 1220848, 1220847, 1220845 & 1220846, whilst those used in the Fuelie are part numbers, 1221851, 1221852, 1221871 & 1221872. If they were the same, they would share the same part numbers.

Comparing the Downdraft pistons with the Fuelie pistons its clear that they are shaped differently and the Downdraft units are more aggressively domed (as a number of different people have already visibly noted and photographed). The Downdraft units are part number 001420801 with a 9.5 : 1 compression ratio and the Fuelie units part number 001420828 with a 9.3 : 1 compression ratio.

You are incorrect when you state the compression ratio difference is 0.1, it is actually 0.2, which is huge when you are talking about translation into performance @ terminal velocity.

Also, the same rule applies to the Swiss Downdrafts, those headers and the box mufflers do not make much of a difference. When Autovisie tested a Swiss Downdraft in 1986 and Autoilustrierte tested another Swiss Downdraft in June 1987, I daresay either car was found lacking.

By the way, if one does not believe the Chief Engineer himself, who do you believe? Personally, I not only belive his assertions, I can see that they have been confirmed multiple times by a number of qualified & competent independent entities, all of which will make a balanced perspective in a good book on the subject.

I will share another thing the Chief Engineer affirmed to me: the 1987 Lamborghini Countach Evoluzione (composite materials experimental prototype) using a standard blueprinted Downdraft engine developed no less than 490 hp, and @ Nardo it bested 200 mph with a standard transmission, although it only had to push 980 kg (2161 lbs).

True, but surely the modification is a compromise that can bring it's own issues with the Bosch FI system.

 

I'm driving very conservatively because I'm using a NOS set of older P7s, but, once I get the new P7s, I will be happy to demonstrate, as well as share the car with you.

 

Agreed, essentially, you can take any car, and modify it to get it to perform better.

Sure, there is no proof that top speed was hindered in the Swiss Downdrafts, essentially I am and have been speaking of top speed.

I just posted virtually the same story a few hours earlier in the other thread, I'm not sure where I heard it from, perhaps from you!

My grasp of the difference of the difference between boxed mufflers and catalytic converters is crystal clear, we simply differ in our opinion of the effect upon top speed, again, I am speaking of top speed.

How a car "feels" to you or I is subjective and not definitive as far as a data-produced conclusive result is concerned. Many Downdrafts have been handed over to qualified & competent independent entities to test them to top speed, resulting in (depending on the tune, 455 - 470 bhp) terminal speeds of 180 - 195 mph, as has been published. Perhaps its time for someone to hand over a Fuelie for a proper top speed test. That said, it would be a test of essentially a modified car wouldn't be conclusive to anyone. The right way to do this would be to test a standard unmodified Fuelie versus a standard unmodified Downbdraft and see what happens. There is a way to find out, I know a number of magazine editors who would be happy to facilitate...

As regards more aggressive cam settings, what settings are you running? I'm confident that if your cam-settings have been modified your top speed will be compromised if you are running on the standard Bosch FI.

The shape of the piston has nothing to do with my declared compression ratio, my source is the factory Chief Engineer, what's yours?

Ditto the parts number assignation, I'm posting from a source I have no reason to question, backed up by the units that have been observed & noted to come out of previously unopened engines.

Perhaps the parts book is incorrect? Or perhaps the Chief Engineer is incorrect? I could ask him.

Very nice, thanks for sharing that. As I said, I do believe the mods most people make will make the car "sound better and be more responsive", the latter translates to a performance differential you can feel on the street. That said, dynoing to see the differences between the various modifications is a good idea.