Speccing a single turbo for a 4.6 RV8

pupp · Post by **pupp** » Mon Jun 11, 2012 9:55 pm

Hi - wondering if I can check with you guys on whether a GT3582 (or clone) would seem a reasonable unit to use on a 4.6 (good BV heads and on Emerald etc with single plenum), aiming for upper 300hp potential with decent spooling and response? Have tried doing some research on the yank sites and these seem to get used in pairs on Chevys etc but do produce (claimed) big numbers. Thanks for any wisdom

JP. · Post by **JP.** » Tue Jun 12, 2012 2:19 pm

Here are the air concumption numbers for a 281ci engine: Link

And this is a typical compressormap of a GT35 :

Lets say you have a 9:1cr blok so you want to run about 10psi max ( is possible on an Alloy block).
10 psi gives you a pressure ratio of 1.68 so turbo spools up around 2800-3000rpm and hit max efficienty at about 4500 rpm.
As you don't come below the 75% efficienty line at higher rpm range there's no real nead of an intercooler also.

But beware, clones do not have the exact trim specs as a real Garrett so this compressormap is only a guideline. I am not saying clones are bad.
GT35 is a uge turbo in mounting size and GT35 is not ideal choise in general as its a missmatch in design ( turbine trim versus compressor trim ). But yeah GT35 clones are cheap and can be found for less then 150 new. Tried one of these eBay link which I won for 150 with shipping. Quality looked decent to me (inside & out) but my engine was to small to spool this ting up to I sold it on.

thewedgeshop.com · Post by **thewedgeshop.com** » Tue Jun 19, 2012 1:01 pm

I think the bigger question is around the specs of the turbo itself and the housings. I think you can get something better than the standard GT35 and for cheaper. If you would like to me spec out what you should be using, I can get you a similar setup for around $750 USD.

I am going to be running a Garret to4e 60 trim .58 A/R O Trim T4 exhaust housing with 3in Vband outlet. This is of course on a 3.5 and I expect spool by 2500-2800 running 10psi.

Below are some more specs on the setup.

Specs
Rover 3.5 (215 cu in)
8:1 compression
93 Pump Gas
ARP head studs, main studs
Stock Heads
Erson TQ20 on a 112 (478 lift, 214 duration at .050)
Cast pistons, rods
Single plane intake
Blow thru Carb (Holley 650)
10-15psi max
Mallory 6 Box (Boost timing retard functionality run off MAP sensor 1* timing pulled per 1LB of boost)
Intercooler Core Size 11"X12"X3" Overall Size 18"x12"x3" 2.5" Inlet & Outlet 3" Core
3 in Mandrel bent exhaust from Downpipe back
160* thermostat
Mallory SS distributor 24* advance with 10* static advance
1 PTE 46mm External Wastegate
1 Tial 50mm BOV
Garret to4e 60 trim .58 A/R O Trim T4 exhaust housing with 3in Vband outlet

Thanks
Clint
The Wedge Shop

Eliot · Post by **Eliot** » Fri Jun 22, 2012 6:23 am

That GT35 seems too big for a low boost 4.6 rover setup. The T04 above seems more suitable, which is akin i think to a GT32.

stevieturbo · Post by **stevieturbo** » Fri Jun 22, 2012 9:55 am

pupp wrote:Hi - wondering if I can check with you guys on whether a GT3582 (or clone) would seem a reasonable unit to use on a 4.6 (good BV heads and on Emerald etc with single plenum), aiming for upper 300hp potential with decent spooling and response? Have tried doing some research on the yank sites and these seem to get used in pairs on Chevys etc but do produce (claimed) big numbers. Thanks for any wisdom

GT35 would be wayyyyy too big for only 3-400bhp.

How much do you want to spend ?

Precision offer a huge range at very keen prices.

http://www.precisionturbo.net/turbochar ... hargers/18

email them with your needs and they can build/spec one to suit.

Most of their smaller units are T3 with 0.48 or 0.63 turbine housings. They're bound to offer bigger T3 housings and it would make more sense.
Failing that, step up to a larger T4 flange 0.68 or 0.82 or something.

Aim for a unit that will do 5-550bhp and you wont be far wrong meeting your 350-400bhp goals with ease.

Something like this with the T3 0.82 housing would work well

http://www.precisionturbo.net/turbochar ... --6076E/64

Powermax Engineering in Cookstown are Precision dealers and would be able to supply ( they're local to me )

If for some reason spool wasnt good, you could drop to a 0.63 turbine housing.

pupp · Post by **pupp** » Mon Nov 12, 2012 1:40 pm

Ok, been a bit quiet on this for a while as have been reading up and researching etc. Thanks for replies.

Reason I initially posed the GT3582 is I have seen one installed very neatly with a 4.6 and also passengered in the car; it behaved/responded well. Against conventional wisdom perhaps, am thinking of trying to stay with the existing long duration/overlap cam I have (306deg plus 112lca) and think the success of this will depend on the turbo not being seen as being 'restrictive' to exhaust flows which I think the GT35 should stand a chance of achieving (I get reversion effects in the plenum anyway at just under 2Krpm and can live with that but don't want to make it a whole load worse)...obviously hoping that when it gets on cam and boosting, I can harness the extra rev range... any views?

stevieturbo · Post by **stevieturbo** » Mon Nov 12, 2012 9:00 pm

Rover V8's arent exactly renowned for their high rpm abilities. What sort of rpm's are you expecting to use ?

Your theory is sound, but in my experience the worst thing you can do on a boosted engine, is use too much cam. Especially if it's a manual gearbox, and you need to have some nice low rpm manners.

Milder cams generally give great results everywhere.

pupp · Post by **pupp** » Mon Nov 12, 2012 9:46 pm

I currently have the limiter set for 6,500 but know the power curve is still climbing there (I admit to being wary of running it harder so far); peak torque is just over 4k but with a very flat distribution (over 300lb between 3,500 and 5,300).... it breathes very well (good big valve heads), feels very happy spinning up, and it just seems a shame to lose that headroom by going backwards on the cam (just about every RV8 plot I see shows them all done and dusted by 5 or 5,250 with massive roll-off right after.... was *just* wanting to start with very low boost levels and see how it progresses, hopefully keping the similar curves and distribution just with more everywhere.

Pistons are late 4.0 units, big journal cross bolted top hat block, cast crank etc. Another reason for wanting to keep the cam (apart from not wanting to strip it out), is that will also keep the effective CR lower which should be kinder.

Am I correct in thinking the higher the A/R, then the less the turbo should restrict exhaust flow off boost?

stevieturbo · Post by **stevieturbo** » Tue Nov 13, 2012 1:53 pm

Again your theory is correct.

Overall the actual turbine itself is the main factor determining flow out the exhaust. The A/R will also play a part, and yes the larger the A/R the more it should flow and less it will restrict ( up to the point where the turbine itself is the main restriction )

I guess the only thing you can do is try it. No matter what, it will work. the only query will be, could it work better ?
But that will always lurk in the background no matter what the build.

You'd just need to do some pressure testing at various locations within the system to see how it is all performing.

pupp · Post by **pupp** » Tue Nov 13, 2012 11:05 pm

Ok, thanks; that's helpful to know I'm on the right track with my thinking at least.

Assuming I go with the GT3582, is it worth going for an anti-surge housing if that's offered? Is the benefit worth the outlay in terms of increasing the chances of decent results?

Also, are there particular 'standard' dimensions for external wastegates (ie a bit like flanges)? I have a particular manifold layout in mind but am not sure whether there is a template 'fit' to fabricate to or whether it's a case of build up the turbo and wastegate assembly and then fabricate round it...? Tried googling this but not getting very far

stevieturbo · Post by **stevieturbo** » Tue Nov 13, 2012 11:10 pm

I would doubt you'll have any surge issues with a large engine and low boost.

Surge housings reduce the efficiency of the compressor, so if you dont need it, dont get it.

And there isnt really any generic fitment for wastegates. You'll need to buy everything before starting.

a 44-50mm w/g should be fine for you. I wouldnt do any smaller than 44mm though.

pupp · Post by **pupp** » Tue Nov 13, 2012 11:25 pm

Righto; again that's good info and appreciated - last one for this evening, I currently use a single wideband lambda probe in the 'Y' piece that collects the two banks... with the layout I have in mind, keeping this location would put the probe directly upstream of the turbo and right in the vicinity of the wastegate inlet pipe off, which all seems a bit busy (not to say hot). Can the lambda be read downstream of the turbo or is that asking for oil contamination causing problems etc?

stevieturbo · Post by **stevieturbo** » Tue Nov 13, 2012 11:41 pm

Generally speaking I would not place a lambda probe before the turbo. It can get too hot, and pressure can affect readings.
The heat will also reduce sensor life.

Fit the sensor at least 12" away from the turbo in the downpipe.

pupp · Post by **pupp** » Wed Jan 23, 2013 11:05 pm

Ok, have plumped for the turbo as discussed above and broadly know where I'm going but, inevitably, further queries arise.... Want to use a front mounted intercooler in the nose void ahead of the rad in a Chimaera. For various reasons, it would be good to have the inlet for this in top with the outlet out the nearside (to pick up the existing ACT pipework to the plenum, which should apparently handle up to 10psi without drama). Assuming pipework of 65-75mm, anything come to mind as being potentially suitable and is this configuration breaking any golden rules on IC layout? Done plenty googling but seems a bit of a black art with plenty of (suspected) rubbish out there...

Moving on to the oil feed, the turbo is a ball bearing job and apparently needs something like 40 psi at max revs, This is about what my serp engine shows so I'm wondering whether I need worry about the suggested oil restrictor that is recommended for BB instals (I guess most candidate cars will have much higher typical oil pressures than our cars)? Also, where would be best to take an oil feed from (filter housing somewhere?), and is the drain best routed to the sump or could low on the timing cover be good for the return assuming the turbo has sufficient height for this (would it not pump out if not)?

Comments appreciated as ever

stevieturbo · Post by **stevieturbo** » Thu Jan 24, 2013 9:00 am

Pipework is simple. Smooth flowing ans short as possible.

Oil feed. It's surprising how small the restrictors on these are. Not sure I'd be tempted to run without, but worst case it should just smoke if you have too much oil. But they really dont need a lot of oil.

Oil return must be gravity fed and not restrictive. Oil return must be above the oil level in the sump

The V8 Owners Forum -

Speccing a single turbo for a 4.6 RV8

Speccing a single turbo for a 4.6 RV8

Re: Speccing a single turbo for a 4.6 RV8

Now to wastegates and oil feeds...