Quad turbo V8 + power limits??

stevieturbo · Post by **stevieturbo** » Wed Jul 22, 2009 11:06 pm

V8James wrote:oh right sorry got my wires crossed slightly

on a 3.9 do you think id be able to get away with t to4e's /t34's with something like a .64 exhaust housing + still be ok?

If above would work out too big id probably be more inclined to for t28's instead of 25's

Again, size of turbo's chosen will depend what sort of power, and power delivery you want.

Personally, for simplicitys sake, I'd just opt for a single.

And there is no point fitting turbos well beyond the capability of the engine, as they will just end up very laggy.

Eliot · Post by **Eliot** » Thu Jul 23, 2009 6:30 am

One of the turbo companies made this, but it doesn't actually work:

Parts were from lawn tractors etc

Aragorn · Post by **Aragorn** » Thu Jul 23, 2009 11:21 am

T34's and T28's are way OTT for your power targets.

You've said you want 400hp.

T34's will manage anything from 340-380 depending on the spec
T28 will manage around 290-310

Running either of those on an engine producing 200hp per turbo isnt going to be particularly nice to drive, with a very high boost threshold.

A pair of T25s from something like a Rover T16 is good for about 250hp each and would be fine and would give nice lagfree power delivery.

Another option would be the K03 turbo used on the Vag 1.8T engines, which will provide 200hp or so with a very low boost threshold.

You also need to remember the NA characteristics of the donor engine. As an example, 1.8L VAG 20V motor will produce 130hp with no turbo. Half a standard rover V8 3.9 will make 80 or 90hp if your lucky, so comparatively the V8 will have a higher boost threshold than the VAG 1.8T becuase the 1.8T breathes better and will move more air to get the turbines up to speed.

If you want 400hp, you need to select the smallest turbo that will give you that power level, if you want it to actually be nice to drive. I suggest a VAG K03, or T25 would be your best option for 400hp.

Eliot · Post by **Eliot** » Thu Jul 23, 2009 12:46 pm

I suggest the o/p learns to calculate the flow requirements and how to plot a compressor map - its really not dificult.

Some discussion of doing twins on a 3.9, utilising Eric's turbo calculator here:
http://mez.co.uk/forum/viewtopic.php?t=436

Boosted LS1 · Post by **Boosted LS1** » Fri Jul 24, 2009 3:53 pm

^ Agreed, hence my initial reply to this thread. Otherwise we'll all be going round in circles.

Eliot, your link didn't open for my pc?

V8James · Post by **V8James** » Fri Jul 24, 2009 5:20 pm

Right ok, ive been playing around with the calculator which Helped me how to understand about sizing a turbo, if im honest im fine with everything else engine wise just didnt know much turbo's + sizing apart from how they worked

A bit of a shame about the effeciency + possibility of a quad turbo setup, would have been nice as i wasnt worried about the extra cost or work envolved

So now im along with others + will go for a twin setup, before i size + suggest a pair of tubbys just need to know a couple of thing

Which is better to start with 3.5 or 3.9?
What power will standard 8.13:1 engine take? already seen about 6psi is max on standard pistons but what about boost on standard rods?

How much boost would i need to see 400bhp? 500bhp?

Apologies for being stuck on a quad setup, i was just fixated by the novelty

cheers

Eliot · Post by **Eliot** » Fri Jul 24, 2009 6:07 pm

Boosted LS1 wrote:^ Agreed, hence my initial reply to this thread. Otherwise we'll all be going round in circles.

Eliot, your link didn't open for my pc?

link fixed

Boosted LS1 · Post by **Boosted LS1** » Fri Jul 24, 2009 7:27 pm

3.5 & 3.9 are short stroke revvy engines but have very weak pistons. I wouldn't bother with those pistons. Look for a 4.0 or 4.6 as these are far better inside. Make sure there aren't liner issues. Or get a 3.9 and rebuild it with custom bowled forged pistons designed for the job in hand. Older rover rods are pretty ancient but seem to handle modest boost, just don't use higher rev limits and remember how many miles they've already done. I've got a set of new carrillo's which I never sold, they're mega strong.

You don't need a lot of boost for 400 hp but it depends on the size of the engine amongst other things. I think you'll need 300 cfm/22lbs of flow per turbo or thereabouts so you can look for turbo's that can flow something like this at full chat.

Mark · Post by **Mark** » Fri Jul 24, 2009 9:00 pm

Ian Anderson wrote:What about the old "E" plate era Diahatsu cherade Turbo engine Tubro

It was used on a 999cc 3 cylinder engine and made over 100 bhp from memory

Ian

IHI RHB52

I fitted a variation of one to my 1000cc motorbike (UK part number VC-19).............was a bit too small so it was fitted with the larger R-20 exhaust housing with a ported waste gate and a bigger compressor wheel due to the silly revs that bike engines go to. It made 209whp at 10psi

Boost started at 4000rpm with the bigger exhaust housing, from memory they come with R-9 R-15 R-20 R-25 the bigger the number the bigger the exhaust housing

This is the compressor map for the original compressor wheel

general pic

Don't give up if it's what you really want to do

Mark

V8James · Post by **V8James** » Sat Jul 25, 2009 12:07 pm

now im mixed up

Some staying dont bother with 4 + then people syaing go for it

Im just playing with the calculator + doing it for 2 + 4 turbos

Ive put down 5500 as a rev limit
I dont know what to enter for compressor efficiency or volumetric efficiency

When you say 22lb of air flow i take it thats where i need the red dot along the horizontal axis?

Am i right in thinking ideally i what to be in the centre island on the map?
James

Boosted LS1 · Post by **Boosted LS1** » Sat Jul 25, 2009 3:31 pm

More or less. You want the 22lbs line to intersect the pressure ratio line somewhere in the peak efficiency area as that's how much air you need when going flat out. Your pressure ratio would be in the region of 1.5 for a 7-10 psi engine. These are fag packet figures but won't be to far off.

At less revs the you'll need less flow but it's still nice to be in an efficient part of the map. You don't want to be near the surge line or choke line.

Eliot · Post by **Eliot** » Sat Jul 25, 2009 5:12 pm

Ok - i'll bite.My link above covers singles and twins, we haven't done a quad one yet so lets play. Taking those figures and reducing the cylinders to TWO gives us the data for a quad setup.

So for a 3.9 at 5500 rpm running quad turbos (achieved by setting the number of cylinders to TWO in the calculator) at 5500 rpm, 10 PSI (pressure ratio of 1.75) - you require a turbo that will produce 8lb/min:
http://www.not2fast.com/turbo/glossary/ ... tyCycle=85

Then lets reduce the RPM to 3000 RPM:
http://www.not2fast.com/turbo/glossary/ ... tyCycle=85
that gives us 4.64lb/min. So you need to find a compressor that will produce that amount of air, somewhere close to the middle of the "island" which is the sweet spot in the middle of the compressor map where the turbo is most efficient.

So I find the smallest Garrett GT turbo map I have and plot the data:

Green line is your 1.75 pressure ratio (10psi) and then the intersections show the air flow at 3k and 5.5k RPM. We can see that we are at least on the map, but not close to the sweet spot - so this in theory would work from a compressor point of view. How well two cylinders would spool that turbo is another matter.
Garrett state that this turbo is good for 50-130 BHP on engines with a displacement of .4 to 1.2L. So that does sort of correlate with the calcs I have done above - which means i'm not talking bollocks hopefully.

And I'll say it once more - twins or single will work best - quads is for novelty value.

And here we are - G12's are £512 from ebay:
http://cgi.ebay.co.uk/Garrett-Turbo-GT1 ... 7C294%3A50

So do you want to spend £2k on four turbos or £682 on a single GT35 that will get the job done better:
http://cgi.ebay.co.uk/Garrett-Turbo-GT3 ... 7C294%3A50
Remember - if they dont spool or you want more power - you need to get 4 turbos modified or changed, whereas a single unit is cheaper to upgrade/swap/modify.

Still want to go quad

Boosted LS1 · Post by **Boosted LS1** » Sat Jul 25, 2009 6:20 pm

Guess that's sorted then

Next.

Ah yes, the engine.

unstable load · Post by **unstable load** » Sun Jul 26, 2009 1:10 pm

There are turbos out there that could do the job. Honda had a CX500 Turbo a few years back, Kawasaki had the Z1000 Turbo and I have seen a 1400cc Perkins diesel that was turbo'd so don't give up on the idea yet.

A bit off the wall, but what about the GM 6.9L?
I know it's a diesel but with that lump you will have huge torque and little chance of blowing the thing up if you overboost it. If you have the space you say you do then sound deadening will sort out the Massey Ferguson sound track nicely.

chodjinn · Post by **chodjinn** » Tue Jul 28, 2009 1:02 pm

Boosted LS1 wrote:Guess that's sorted then

Next. Ah yes, the engine.

3.9 will take around 300bhp in standard form, with full ARP block/head bolt kit, with 36cc heads and composite gaskets. Mine should have about 320bhp running two T04B Rotomasters at approx. 8psi. stage 3 heads, turbo cam etc. Turn the boost up much more and it will go bang, hence why I'm building a forged 3.5 xbolt engine (if you make me a good offer I may sell it!).

Stevie turbo got circa 500bhp out of a 4.6 with similar spec, but Stage 4 heads, think he ran two T3 turbos at 15psi.

Either way it's gonna cost a lot of money, and if you skimp you will regret it, that is the Rover way lol.

As for turbos, I'm seriously thinking of going to a single set up on the 3.5 in a couple of years. High revving monster with a Holset HX40 or thereabouts. Altho I'd love to stick a HX52 on just to see what it does lol.