Turbo Charging a V8 advice needed

Hello Guys, I've been floating around for a while taking advantage of the abundance of information on this site but never felt the need to post up until now.

I am currently in the early stages of a full rebuild of my Defender 90 300tdi which I intend to change to a V8 with some interesting power.

I have a 3.5 carb (twin SU) engine which I have already striped down, cleaned and in the process of porting the heads (although probs not necessary for turbo). Still yet to purchase all the bits to put it back together.

I am also acquiring a 3.9efi (not serpentine) as it comes with the auto gearbox that I want as i've heard they can handle more power. Now this engine at the least has a blown head gasket which I don't mind fixing im just hoping its not the liners but for the purpose of this thread lets just assume I can fix it up. (may do a rebuild on this too)

Whichever engine I don't use will be fixed up either way as a spare in case the turbo engine goes tits up!!

Anyway on to turbos... I really want to give one of these engines a fair amount of power and am fairly confident I can make either engine work with a turbo, but unfortunately I cant seem to find a post that completely documents the process of doing it to either engine (unless ive missed it).

Im not planning on shoving loads of boost through the engine but I would think even a little (5-10 psi) would make a substantial difference.

I wont be using this as an everyday car, it is going to be my toy but I would like it to last. Ive read that fast spooling turbos are good for torque but I have no idea what turbos to use (guessing a couple of 2litre ones)

Im happy to fabricate all the necessary metalwork like the manifold, exhaust and any brackets ect

I have also read up on a mini forum of how to seal the SU carbs and it seems fairly straight forward but im not sure about jet sizes and set up. I may just get mechanic in for that bit

The questions I have are;

1- Which engine would be better to use (I think 3.5 is lower compression??)
2- Which is the cheaper/easier option, carb or injection
3- If injection, would I need a Megasquirt set up and do I need the whole kit (£950!!) or just some of it.
4- Can the SU Carbs go on the 3.9
5- How would you guys go about doing such a project.

Would be really grateful for any advice on the matter as I really want to do it right.

Once I have done it I will post up how I ended up doing it for others to see, just in case anyone else is just as mad as I am. It may just make it easier for them.

Sorry for the essay

Thanks in advance guys

Steve

Speak to ZEN

Personally I binned a rv8 for something better

As above, zen is the chap you need to have a word with regards to boosted Rover V8s. (He's got a supercharged 4.6 using an M112. Fantastic!!!)

Ignoring all the "blah blah its easier to get more power with a different engine" and going on the basis that this is a project you want to do because you can then I'm all for that. So here are my answers to your questions.

stevelucas18 said:

1- Which engine would be better to use (I think 3.5 is lower compression??)

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The 3.9 will have more power than a 3.5 and is easier to get power from. The 3.9 revs quite nicely with its bore/stroke ratio so that could be handy if you want it to rev up and spool up your turbo(s) quicker. Compression ratio at these levels I don't think should concern you too much. the 3.9 will have 9.35:1 CR and the 3.5 either 9.35:1 or 8.13:1 CR. You could argue that its safer to boost the lower CR one but do you want a lazy V8 when you're not on boost and before the turbos spool up? If you fitted water/methanol injection or even an intercooler then you can boost the 9.35:1 CR engine. You might get away with a few psi of boost without water/methanol injection but I think it would be wise to fit it and get a few more psi because you can!

stevelucas18 said:

2- Which is the cheaper/easier option, carb or injection

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In my opinion I'd go for injection. You could put a turbo on each side and have suck through SUs... or blow through SUs... But as you've already mentioned megasquirt then that sounds like you're on the right track. Complete control over fuel & ignition will make tuning it far easier than having to deal with needles in carburettors etc. Uses a MAP sensor so can detect when on vacuum/boost/etc. Control over ignition is handy, retarding the ignition when on boost, etc

stevelucas18 said:

3- If injection, would I need a Megasquirt set up and do I need the whole kit (£950!!) or just some of it.

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If you've paid for it you might as well use all the features! What kit were you looking at that is £950? As above, complete control over your engine is really useful if you're bolting on a turbo or two!

stevelucas18 said:

4- Can the SU Carbs go on the 3.9

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Its just a case of removing the EFi inlet manfold and fitting the SU carburettor inlet manifold. You could put the SU carburettors on the 3.9 and then rejet them to suit if needed. But why would you do that? A step backwards I think.

stevelucas18 said:

5- How would you guys go about doing such a project.

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If I was turboing a Rover V8 then I'd do it as mentioned above. EFI is the way forward.


Bloody good luck with your project, I look forward to seeing updates!

Thanks for the quick replies. with the mega squirt I was looking at these Megasquirt for V8 engines - Complete kits but a fair bit of it looks un-necessary to make it work, I think the whole kit I was looking at is more for waterproofing maybe? or do I need all of it? surely it doesn't have to be that expensive.

I forgot a big question and that is "what Turbos to try and get hold of??" im thinking of searching the local breakers/scrap yards but im not sure which cars to look for... any ideas? I guess something common so I can find two the same.

oh yeah and I will be using an intercooler...mounted somewhere lol

stevelucas18 said:

Thanks for the quick replies. with the mega squirt I was looking at these Megasquirt for V8 engines - Complete kits but a fair bit of it looks un-necessary to make it work, I think the whole kit I was looking at is more for waterproofing maybe? or do I need all of it? surely it doesn't have to be that expensive.

I forgot a big question and that is "what Turbos to try and get hold of??" im thinking of searching the local breakers/scrap yards but im not sure which cars to look for... any ideas? I guess something common so I can find two the same.

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Waterproofing is just one of many benefits of megasquirt - what do you think is unnecessary?

You can MS your V8 for cheaper if you buy the bare minimum, source parts yourself, fabricate mounts, solder PCBs and wire the loom yourself etc. But those kits are complete and include everything you need. So its more convenience than anything I guess. Up to you if you want to save the £££ and DIY the bits you can.

As for suitable turbos. I haven't got a clue - There seems to be a wealth of information if you know where to look. Threads like this pop up The V8 Owners Forum - :: View topic - Rover v8 3.9 Twin Turbo Build - Turbo Selection

I guess finding the right one is going to be interesting!

Out of curiosity - what made your mind up on turbo(s) or supercharger?

Yeah I was thinking nonsense out load then looking at it again it does add up to a lot of bits and bobs. Probs will be easier to just bite the bullet and buy it.

I think turbos just seamed like a cheaper route than supercharged but I haven't really looked into supercharging it. I assume it would be easier to get hold of some cheap used turbos than finding a supercharger to fit. I always knew that getting the fuelling right would unfortunately be the tricky/expensive job turbo or supercharged.
All in all though the thought of building a twin turbo V8 gives me goosebumps haha

Potentially risky trying to find two used good turbos that are suitable. Or buy new or buy used and get refurb'd. Lots of options depending how you want to do it. Although anything can be done given enough time and looking in the right scrap yard or garage.

If you went supercharged, then eaton superchargers pop up on eBay quite often - your choice of an M62, M90 or M112. (M45 is far too small for a Rover V8). I think an M62 can do up to 4L engines so might be pushing it too much if you used an M62 on a 3.9. Could get away with an M90 on a 3.5 or 3.9 but M112 would give you more potential as its the biggest and can move the most amount of air. (zen has an M112 on his 4.6L Rover V8).

I do like the idea of a twin turbo V8 rather than supercharger - guess it depends what you want though at the end of the day. Goosebumps indeed!

hmmm..are you serious or dreaming??

if dreaming...then fine, but if serious then it will cost a few quid..

i would not go for turbo, but supercharge, but if want turbo then i woukld be going for twins..ie like i have in garage for next one a pair off rover 25 diesels..they are small..nice and small so will give boost at low rpm and according to map drop out at about 5500rpm..more than enough for rv8.

i would go 3.9 or bigger..but then top hat so add£1k, or to keep cheao 3.5 or even 3.9 but expect to be a throw away engine when it dies..(espicaly 3.9)

you will need new cam and followers rocker shafts and arms.PERIOD..they will be fecked.

auto box will NOT take more power unless you go for zf24..but that envolves mods to fit it..


dump carbs..they wont work unless using drawthough and that means sucking fuel mixture though hot turbos..not ideal..

meaquirt is excellent..go for ms3x it costs more but allows you to use full squential in future ++has many added facilties for using boost..lauch control.knock sense etc..well worth the extra cash inho

zen said:

auto box will NOT take more power unless you go for zf24..but that envolves mods to fit it..

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I thought everyone recommended auto for big V8 power, but on a land rover I don't understand it, as the gearbox can take the torque on low range which must be far greater than using on high.

Hence, big power V8 predominantly used on road in high range - don't see the issue.

Having said that, its just a thought process, not a tested theory. I have done a few traffic light grand prixs in my high compression 4 litre carb'd V8 110 manual, and it does spin all the wheels off the line when asked. I'm just testing the drive-train, I know its bad for it but it feels so good.

zf22's just die with any power..the lt77 r380 and espically lt85 are really under rated..i run 450hp though the lt85..used to run a 3.3 6 pot 2 bar boosted lpg injected tdi in front of the lt77 for years..9and they are so slated!!)never any problems except for smoking the clutches!!..

anyway..thinking more on this..

carbed 3.5l =130hp ish..so adding turbos =200 if lucky..so cheaper and better to just fit a 4.6 with new kent cam and headman headers + megasquirt (or fit gems ecu once unlocked)..one would have to rebuild the 3.5 with same cost as 4.6, but this way one would get circa 250hp plus more reliable, better power delivery etc..

so why bother to boost the 3.5 ?

zen said:

so why bother to boost the 3.5 ?

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Because you can get 250bhp from a boosted 3.5.

Why? because you can

Why did you supercharge your 4.6? Because you could?

missing my point...
and yes i agree ehy/ because you can...but
.cheaper easier just to throw in a 4.6...to get 250 from the 3.5 will cost lots....now if after power then boost the 4.6..do if proper like?

I agree - if after power yes, its easier and cheaper to throw in a 4.6 and do things with that.

But if you're like me then for some strange reason I just like the 3.5 and am not concerned about all out power so am happy to do with what I can with a 3.5.

thats fine..but its not you thats after turboing a 3.5..

the amount of work is massive, fabbing up headers,installing efi or modding cabs etc

The auto you are acquiring is rated at 280 lb ft Max torque.
So it will be on borrowed time.
Mine lasted about 3 years before failure with a tuned 4.6
I guess it was getting closer to 300ftlb

zen said:

hmmm..are you serious or dreaming??

if dreaming...then fine, but if serious then it will cost a few quid..

i would not go for turbo, but supercharge, but if want turbo then i woukld be going for twins..ie like i have in garage for next one a pair off rover 25 diesels..they are small..nice and small so will give boost at low rpm and according to map drop out at about 5500rpm..more than enough for rv8.

i would go 3.9 or bigger..but then top hat so add£1k, or to keep cheao 3.5 or even 3.9 but expect to be a throw away engine when it dies..(espicaly 3.9)

you will need new cam and followers rocker shafts and arms.PERIOD..they will be fecked.

auto box will NOT take more power unless you go for zf24..but that envolves mods to fit it..


dump carbs..they wont work unless using drawthough and that means sucking fuel mixture though hot turbos..not ideal..

meaquirt is excellent..go for ms3x it costs more but allows you to use full squential in future ++has many added facilties for using boost..lauch control.knock sense etc..well worth the extra cash inho

Click to expand...

Agree.

This does sound like a lot of work - I agree with everything said here.

One good source for turbos is Saabs.
Choose one from a 1994-1998 2.0 turbo car if you can.
They are generally very reliable, so you are likely to find cars with them in the scrap yards for little money.
The turbos were the same on the 2.0 low pressure and high pressure turbo cars.

But not the 9-3 & 9-5.
If you are using a turbo from these, don't use the low pressure ones - they fail regularly... Stick to the high pressure turbos ( lpt cars had a small "t" after the engine size "2.0t", the high pressure cars had a big "T" "2.0T" or were fitted to the aero models ( but rare though).

The Saab 900's peak torque was at 1800 rpm ( yes really!) and hard pull through to 6000 rpm. Bit laggy though, but this is the fun of turbos!
In non turbo form, the 2.0 saab delivered about 130 BHP. turbo, but no intercooler boosted it to 150, and 186 BHP with intercooler, and chipped easily past 220 bhp.
Two of these should be quite nicely matched to a rv8

How would I approach it?

I wouldn't use anything other than a top hatted block, unless it was a 3.5.
The liners will slip, and you have to tear it all down again...

Also, the cross bolted 4.0 and 4.6 are a much nicer ( more robust) starting point.

EFI will be easier to manage, because you will have full control of the fuelling.

Get the thing running reliably first - without the turbos,
When you are happy you have mastered the megasquirt, then go for pressure charging...

Not sure what I'd do with the transmission.

I usually opt for autos, but a good turbo install is crying out for a manual - r380?

Let us know how you get on.

The trouble with single turbo setups in the UK, is finding a turbo of suitable size.

Remember boost is a measure of resistance, not flow. So putting on a tiny turbo from a 1.5-2.0 engine @ 8psi will not give the same cfm (air flow) as a large turbo @ 8psi.

This will translate into very different amounts of power and power curve.

Twin small turbo's are likely the only economical way in the UK. But may still boost too quickly and not deliver the higher rpm performance.

Personally I'd look at the rear mount style of turbo, assuming you could tuck the pipe work up out of harms way off road (Google STS Turbo's for an idea how this is done). Rear mount might not give the best throttle response, although gives good options for not needing a dedicated intercooler setup. Biggest bonus is, pipe work is easy to fab and you don't need costly custom exhaust manifolds.


I think power, performance and even reliability on carbs will be limited. It's all possible, but just lots of faffing.

I've debated many times turbo'ing my TR7 V8. But the cost vs the gain and hassle never seem to really add up.

Going Megasquirt would certainly give a lot more options. But by this time you are really starting to wrack up the pennies. And tbh things like an LS1 swap are likely to be similar costs. And a stock LS1 will spank pretty much any Rover V8 in almost any guise unless unseemly amounts of hard earned have been ploughed into it.

Oh yeah. I truly don't see the point of switching to an auto. An auto will be a lot less fun and blunt the performance. If you are looking at this mod for speed and fun, then an auto isn't the way IMO.