More New Scrambler Details

Dave Milne did pass the time by typing:

4.0l HO is 8.8:1 actually :) I stuff another 5.5psi into it with just the stock pulley. Any more and it would need intercooling or larger injectors.

I use a eaton, roots type, blower, always turning even at idle. The good part is it doesn't heat the air near as much as a vane charger like the paxton does.

wow you run a non intercooled setup? how much boost aqre you running? thats a nice compression for f/i but i would still be nervous without any sort of intercooling.

if its space constraints, you can run a small water to air setup.. costs will be around 200 if you can weld aluminum (for the casing) youself.. with a 2 gallon setup, a small 6x8x2" core should be sufficient since as you say, your particular s/c isnt heating up the air too much (any idea exactl;y how much? i know turbo's can add 70-100 degrees to the intake charge depending on boost, but a properly intercooled air-to-air setup will return that back to within 10* of ambient. a w/a is good for low boost since its more consistent, less dependant on vehicle motion... but wont cool it off AS much as a large a/a.

*(unless you run a water/aclch mixture, and pre-cool it, with an ice chamber, etc)

-Steve 98 TJ

didn't make myself clear - I meant turbo engines in general (e.g. Ford Cosworth, Subaru Imprezza turbo are both 8:1)

True, and also to keep the heat => early detonation down.

Dave Milne, Scotland '99 TJ 4.0 Sahara

: > didn't make myself clear - I meant turbo engines in general (e.g. Ford : > Cosworth, Subaru Imprezza turbo are both 8:1) : > -- : > Dave Milne, Scotland : > '99 TJ 4.0 Sahara

Depends on the design. Many turbo designs can develop lots of boost at relatively low rpms. This is the whole point behind twin sequential turbos.

2 smaller turbos can spin up at lower exhaust gas pressures than one larger one. Also, a centrifugal supercharger needs high rpm to build up decent pressure too.

I have owned 2 different SAAB 9000 full pressure turbos. They both develop full boost by the time they reach ~2500 rpm. They have a considerable amount of torque for their low 2.4 liter displacements. 225 Hp and 258 ft/lbs in stock trim and with a chip they can be coaxed to 260 Hp and 287 ft/lbs easily with no other modifications. These engines were very torquey and did not have very high redlines. They are also not high tech engines made from unobtanium. They were early '90's vintage engines that routinely ran 250-300k miles with only a timing chain or head gasket in the interim. But the engines were designed with forced induction in mind, unlike strapping a blower on a pushrod V-8.

What I'd really like to do is put a modified roots type blower on an 8 cylinder 4.5 liter BMW engine (which makes ~280 hp 320 ft/lbs normally aspirated). I'm sure that would be more than a handful.

-Fred W

Its up to 333 bhp at 6,100 rpm now ( 4.4 litre in the 745i).

Dave Milne, Scotland '99 TJ 4.0 Sahara

Fred W. did pass the time by typing:

Considring my friend at work drives a BMW M5 with the 4.5 engine and wants me to do the blower install... I'll let you know. :)

Of course he has to buy the dang thing first.

His previous car, now owned by another cowerker, was a 300ZX Twin Turbo. Dual spools are a blast but only if both are working correctly. And (deleted) was that a beast to work on. Everything crammed in so dang tight there isn't even room to use a wrench someplaces.

Umm, actually he is. When you compress the air it becomes hotter. Thermodynamics and all that stuff...

-Fred

yes, that's the newer V8 engines and would be even better though more $$. I was referring to the earlier engine in the 540's.

-Fred

That will definitely be a great setup, though your friend will certainly be much lighter in the bank account.

-Fred W

its the magical BMW 286 bhp thing again !

Lets see now:

the '85 635 CSI had a 3.5 i6 , the '89 840/540 to which you refer has a 4.4 v8, the M3(E36) of '93 had a i6 3.0,

each of which produced 286 bhp !!!

Dave Milne, Scotland '99 TJ 4.0 Sahara

: >

: > Dave Milne, Scotland : > '99 TJ 4.0 Sahara : >

: : yes, that's the newer V8 engines and would be even better though more $$. I : was referring to the earlier engine in the 540's. : : -Fred : : : --- : Outgoing mail is certified Virus Free. : Checked by AVG anti-virus system

Version: 6.0.516 / Virus Database: 313 - Release Date: 9/3/2003: :

Goat Crapp did pass the time by typing:

5.5psi stock, 11.5psi with race fuel or at altitudes above 5000ft with 92 octane. Oklahoma is too low to run 11.5 without water injection and Bilouxi (keeser afb) is almost too low to run at 5.5.

Roots blowers don't heat the air near as much as vane types do. Take a feel of almost any vacuum cleaner exhaust. That heat is mostly due to the inefficiency of the impeller.

5.5psi compression of air at sea level increases temp by... (where is my thermodynamics book?) ..search.. ..search..

Ok.. that would be about 150ºF increase for ideal where a vane type with about 65% efficency would be 259ºF increase.

There just isn't room for an intercooler with my setup. Water injection is the only viable alternative. I am thinking about bringing some cool air back into the engine bay or installing the hood vents from the 5.9.

Much more than that, try almost 200ºF without intercooling.

Yep.. only problem is space. Pics are on my site. This is the casting that adapts the blower.

Twelve cylinder. God Bless America, ßill O|||||||O mailto: snipped-for-privacy@aol.com

what is ?

Dave Milne, Scotland '99 TJ 4.0 Sahara

Only for the first few feet with a blower... if that long.

Approximately 10/10/03 12:04, Dave Milne uttered for posterity:

You still get adiabatic heating just from compressing the air, which is where the significant heat in an exhaust turbocharger style comes from as well. Only time you get much heat transfer with an exhauster is at low speed and idle...where it cokes your turbo bearings regularly if you don't give it a cooldown or use watercooling for them.

Approximately 10/10/03 12:44, L.W.(ßill) Hughes III uttered for posterity: