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tips, technology, tools and techniques related to vehicle driveline components

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soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

Main British Car:


Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 09, 2021 03:36PM

Im going to fit a single turbo to MGB the engine is stock so no high revs, its for a street car, do you think the specs for this turbo is ok?

Specification
Exhaust Inlet (Turbo Manifold) Flange: T3 T4 4 bolt Flange Patterns
Exhaust Outlet (Downpipe) Flange: V-Band Flange
Turbine Trim: 73
Turbine Inducer Diameter: 65.5 mm
Turbine Exducer Diameter: 55.9mm
Turbine A/R: 0.63
Compressor Trim: 44
Compressor Inducer Diameter: 50.5 mm
Compressor Exducer Diameter: 76 mm
Compressor A/R: 0.5
Its a little on the tight side, but I want the power lower than higher in the powerband, any one have any thoughts? thanks


88v8
Ivor Duarte
Gloucestershire UK
(837 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Which Turbo for 3.9 Rover V8?
Posted by: 88v8
Date: March 10, 2021 05:18AM

You in the UK?
Save yourself much bother and experimentation, buy this with its 3.9 Turbo Technics motor, and do an engine swap
[www.ebay.co.uk]

Ivor


soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 10, 2021 08:11AM

Thanks for that but no, I have a fully rebuilt cross bolted 3.9 with studs, oil mods etc, its in the car & ready to go,
Its not the first turbo engine Ive built so it wont take much to get it working well.

I have the above turbo in stock along with a GT30, which I could use, but it would work better higher up in the RPM, for a strret car Im thinking the other Turbo would be a better choice.


88v8
Ivor Duarte
Gloucestershire UK
(837 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Which Turbo for 3.9 Rover V8?
Posted by: 88v8
Date: March 11, 2021 04:53AM

I ran a Renault 5 GT Turbo for 13 years as daily driver.
Great fun, but the on/off switch at 3,000 rpm is not exactly relaxing !

Ivor


MariaMitchell
MariaMitchell Mitchell

(1 posts)

Registered:
03/12/2021 08:53AM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: MariaMitchell
Date: March 12, 2021 08:58AM

In my opinion, it is quite acceptable. I would like to test it!



Edited 2 time(s). Last edit at 03/13/2021 11:52AM by MariaMitchell.


soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 13, 2021 06:50AM

Ive found SU carbs correctly set up in a blow through arrangement work great, with out flat spots & great MPG,, the HIF44 or the larger 2" version are one of the best carbs every made,


88v8
Ivor Duarte
Gloucestershire UK
(837 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Which Turbo for 3.9 Rover V8?
Posted by: 88v8
Date: March 14, 2021 05:39AM

Quote:
"so16"
Ive found SU carbs correctly set up in a blow through arrangement work great, with out flat spots & great MPG,, the HIF44 or the larger 2" version are one of the best carbs every made,

I agree.
The challenge nowadays is going though all the needle profiles to correct the AFR, or indeed grinding your own needles.

There was a chap on the TR Register forum with a blown 6 who did that.
He had a sensor in the exhaust linked to a laptop so he could monitor the AFR.
He took off the bonnet (hood).
The carb had a modded top to the dashpot with a little rod sticking out through it.
The rod was marked in inches.
A helper watched the rod to see how high the dashpot was sitting for a given AFR, and from that he could work out which part of the needle was in the jet, and grind it down a little (with emery paper IIRC) if necessary.
He started with a weak needle (fatter).
Then rinse and repeat until correct.

That was a suck-through, but the principle would hold good for a blow-through.

Then of course there's which oil to use in the damper, and what colour spring.
A labour of love, perhaps.

Ivor



Edited 1 time(s). Last edit at 03/14/2021 05:41AM by 88v8.



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6008 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Which Turbo for 3.9 Rover V8?
Posted by: BlownMGB-V8
Date: March 14, 2021 02:35PM

Funny story, my 3rd 215 engine in the B I built 8-4-1 headers and installed a Jetfire turbo with a 2" SU in suck configuration and had a huge gaping hole in the hood that I was shaping a scoop to go over. So I was tuning the carb and being in about '91 didn't have all this fancy equipment like wideband sensors and such to play with, so I had my best friend climb in the passenger's seat and while I blasted up and down Cincinnati's Hospital Hill he stood up, hunched over the windshield to which he held on with one hand and with the other adjusted the carb. Every now and then he reminds me of that, I'd say it made an impression!

These days I can't even remember what we were adjusting. But I sure do remember him doubled over the windshield while I let 'er rip.

Jim


soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 14, 2021 04:50PM

I have a large collection of Su needles a number of carbs, & plenty of experiance tuning these find devises, both NA & blow through, Ill have it nailed down in short order!


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6008 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Which Turbo for 3.9 Rover V8?
Posted by: BlownMGB-V8
Date: March 14, 2021 05:33PM

I was turning my own needles on the lathe and drilling out the main jet. The trick is to get enough fuel at WOT and not too much at idle. Takes a lot of taper and a very fine tip.

Jim


soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

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Re: Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 14, 2021 08:32PM

A while ago I did a 3 litre v6 blow through turbo using twin SU's, I have a set of needles that that build used, so Im allready off to a flying start, that engine made big power & ran like a Swiss watch, an old timer I know has a cutting jig for leaning needles, setting this up wont be a problem.


turbodave
dave cox

(60 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: turbodave
Date: March 15, 2021 08:39AM

If you post the compressor maps, or links to them, I'll put them in my spreadhseet and let you know. I'm surprised you'd want to go single though; so many I4 engines around that have very well matched turbos that are crying out to be used as twins on a RV8 - the GT17 from a saab 9-5 for example, or the GT2056 from the iveco, or for something bang up-to-date, the twin-scroll garrett used on the 2,3 ecoboost is a boost monster....

I've spent many years playing blowthru with SUs and agree they will be a good fit. The key is to use the MG turbo plenum (or an exact replica thereof). These look a little basic and odd with the brass restrictor ring, but nothing works better - and everything else is worse. When used with the MG plenum, needles are easy to file, and don't need to be as radical as you may think. Malpassi make a twin outlet reg (as used on the esprit) that is the best unit for SUs - but you do need to use a return line with zero restrictions (or just use a 1/4 feed and 5/16 return) - or if you use 5/16 for both, put a restrictor in the line just before the reg to restrict the flow.

What you said about filing the needles - you'd need to have the "dashpot height indicator" in a glass tube for blow-thru. It's been done before.

I would recommend doing the tee-piece trick to pressurise the float bowl - even though the internal carb porting is meant to allow this, and if you have the shiny black bypass hose on the carb, block it off (as well as the butterfly poppet valve).


soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 15, 2021 10:16AM

Thanks for the offer, but I dont have any maps these are chinese garrett copies, its false that they are rubbish Ive used them a few times before & allways had good results.
I really like the low restriction of the bigger turbine but this is a street car for just smoking about in, so Im torn between low end punch or the top end rush.
If i do use the bigger turbo I wont use a waste gate, Ill vent the boost pre intercooler, with a large turbo just get the thing spinning & keep it moving, this can work very well with out the chokeing effect of a smaller turbine housing.

Im using a single turbo because of lack of space its an MGB. I have a large intercooler using 2'5" pipes its really tight for space.

Ive allready made the plenium & Ill be using a Pitot Tube to pressurise the float bowls, the carbs Ive fitted seals to the throttle shafts, the inlet valves have been modded to allow more fuel in, butterfly poppet allready blanked off. I agree the Malpassi is my choice for fuel reg'

Im also using a Crane HI6 multi spark ignition with a MAP much better than the MSD stuff I rekon...


turbodave
dave cox

(60 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: turbodave
Date: March 15, 2021 11:57AM

The fastest A-series mini in the UK (Jim Lyons) uses a china CHRA - as do I - so no need to convince me of anything in that manner.

There must be a map of the turbo its based on - the compressor map, not the wheel diameters are how you define the fit of the turbo; the wheel diameters tell you (broadly) what the ultimate flow will be.

The pitot tube you describe for the SU's may not give the best results - heaven knows I feel like I've tried so many different versions, but always arrived back at the design of the stock brass restrictor tube; it looks odd, but is truly effective and was clearly arrived at by design not accident.



Edited 1 time(s). Last edit at 03/20/2021 08:55AM by MGBV8.


turbodave
dave cox

(60 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: turbodave
Date: March 15, 2021 03:03PM

I found a T04E 46 trim Garrett map and did some plots, assuming 3.9l, 5000rpm redline, and with some generic assumptions.

First is 7psi, then 10psi, then 15psi.

As you can see, the 46 trim (remember yours was listed as a 44) maxes out, pretty much at 5000rpm and 10psi. You can drop to 4800 rpm, and hit 12psi, but you're pretty much maxing at 36/37 lb/min - which is around 360/370 hp to all intents....
This may suit you down to the ground, but it's really only tickling the surface of what you can boost with this turbo - more boost won't gain you any more. But 360hp is still a lot of fun!

However - the complete lack of any turbine maps, and how low-down the turbo is working in its available range, suggests to me the turbine will be way too large to make the boost at 2500 rpm. I suspect you'll not start seeing any boost until 3500rpm, which leaves a pretty narrow power band....
personally, I'd be looking to see what the next size up is, looking also at the turbines, while trying to get the smallest turbine possible.



7PSI.jpg
10PSI.jpg
15PSI.jpg



Edited 3 time(s). Last edit at 03/15/2021 03:24PM by turbodave.



88v8
Ivor Duarte
Gloucestershire UK
(837 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Which Turbo for 3.9 Rover V8?
Posted by: 88v8
Date: March 17, 2021 05:15AM

Sometimes posters come up with aspects one hasn't thought of. That's the power of a forum. Not that everyone is suited to conversations on a forum.

Anyway, for most people, running a wastegate is 101 nowadays . Yes, one can run without, by choosing a turbine that will only reach its maximum revs and boost at the engine’s max RPM, but most engine builders would regard that as self-flagellation.
However, as a fan of vintage machinery, I like old skool, so good for you.

My thought... a single turbo takes longer to spool up, but if that's all you've got room for....

Ivor



Edited 1 time(s). Last edit at 03/20/2021 08:56AM by MGBV8.


turbodave
dave cox

(60 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: turbodave
Date: March 24, 2021 02:24PM

Did admin delete his later posts?


MGBV8
Carl Floyd
Kingsport, TN
(4042 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: Which Turbo for 3.9 Rover V8?
Posted by: MGBV8
Date: March 26, 2021 09:17AM

Yes. This has always been a civil & respectful forum.


turbodave
dave cox

(60 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: turbodave
Date: March 26, 2021 10:44AM

Excellent work.


soi6
Tim east

(61 posts)

Registered:
06/24/2018 06:40PM

Main British Car:


Re: Which Turbo for 3.9 Rover V8?
Posted by: soi6
Date: March 26, 2021 05:43PM

Hang on a minute, I say I don't want some ones advise, they respond with some snotty reply......

Then some one else says I'm not prepared to listen a to anyone on a forum, then says I'm using some old skool technices?????

The two people on here are making incorrect assumptions to what I'm actually doing, then when I don't take their incorrect advise they get shirty about it.....You need to reassess what being said here!
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