Explain the MD321 turbo?
 

Over the past year or so I've noticed a lot of threads talking about these MD321's and from the sound of things, they are the do anything, go anywhere turbo. What's so good about them that's so different from other turbos like TDs, VFs, GTs etc? I'd always assumed that a 'big' turbo gives big boost at the expense of spool point and/or lag, and a small turbo gives better response at the expense of top end power. In other words, like anything else in automotive tuning, there's no such thing as a free lunch. Obviously there are hybrids which mix and match cold and hot side components to try to improve characteristics but there is a limit to what you can do.

So what's so great about the MD321 that has never been seen before? It seems to do everything - big boost, low spool up point, low lag, full airflow to the redline etc. If this is really the case, how does it do it, what's the technology, is what I'm saying really?

The MD321 is a VF/GT30 hybrid , it's exact specs are regarded as secret and there are a few variations...
In essence you can buy alternatives that will give you similar results and again there are variations on all of these..

A good question to ask on 22B?

They cost a lot more than a 20g so I presume there are lots of 'adjusted' parts in there that are hand fettled.

I've wondered this as well, what makes the MD321 series so good?

In reality are they any better than the other Garret Hybird's on the market by the likes of RCMS and Scoobyclinic??

I hav had mine for 2 month now , on my builts 2.5 it is awesome , spool quicker than the vf34 that i had on my 2.0 before , make much more power /torque(460-480/same).
its a MD321T :)
highly reccommended :thumb:

Chuckled when I saw this thread as I've been thinking about upgrading my current 18G turbo to the MD321 for a few weeks now. As Graham says 22B is a good source of info regarding this very subject but I've not found it conclusive by any means. A lot of the associated threads seem geared towards 2.5 engines and the like so I'm still unsure whether it would be worth the outlay on my 2.0.

Will keep my eyes on this thread!

My MD321T was awesome with my 2.35... Good turbo that bolts in standard position...

Questions for Bighead

At what Revs does it make 1bar of boost?
At what Revs does it make full boost?
What revs does it hit max torque?

I have a 2.5 20g and would like to know if your setup equals or betters the boost and torque targets for revs

Andy

Plenty of info on 22B, comparisons against 20G's etc

Cheers I'll have a look.

Andy ....believe me the MD will out perform the 20g at every departments :)
regarding yr question ...its all depends on the mapper , I can tell you that I run out of gears to change .......I can pull 6th gear at under 2000 rpm !

Had the APS SR40 turbo on my 2.0(before my 2.5/Md321T), imho the MD is a much better turbo costing a few hundreds notes less :)

you need the MD321H for yr 2.0(MD321T is better on spool up on the 2.5)
the "H" model will be as quick (if not quicker)than a VF34 on a 2 litre, but it will make 400bhp wheres the VF will only do 340-360 bhp !

So in essence the 'T' variant is nicely suited to the 2.5, whereas the 'H' is better for the 2.0. No wonder it's getting popular if it can make 400 in the standard position and spool up like a smallish VF.

Regarding the 'secret' formula, surely all one needs to do is look at the compressor and turbine housings and take them apart to see what the crack is? Or ring up Turbo Dynamics?

They wont tell you, They are Lateral Performance designed turbos built by Turbo Dynamics, alot of effort went into there design (still ongoing)... just buy it and be happy :)

Silent you've got in in one there :thumb:

Hello Conrad....Happy new year :)

sry to hear you've sold TheRacingLine ......

I believe the T is pretty good on a newage with AVCS heads and even better if it is a built 2.0l

The spool / response will always be better on a 2.35 or 2.5 for the MD321T.

If you are looking for best spool and are not as worried about top end figures, the 321H is probably best.

Would be great to get Bob Rawle's comments on this, as he has mapped quite a few MD321T and H's. (added: or Andy F for that matter)

Not sure of the secret formula though.

A 321T ona built 2 litre engine is phenomenal. With the 2 litre's high revving nature, the turbo just keeps on boosting all the way up to the red line. i had 2 bar at 8k revs - awesome. On race fuel it made 504bhp and 486lbft on my 2 litre - Nice :D

mine being 1 of them :thumb:

Well don't keep us in suspense then mate! :norty:

Mike, thanks, Same to you, hope your well! Time to move on, its in good hands though ;)

Back on topic....

I believe Andy F has( or had) a 321T on his road car
:)

I love the comment about it being a bolt on - it wasnt on my sti5 - had to angle grind off some metal on the car first for it to sit flush (well Dave Harries did for me :-) )

Its laggy on a 2 litre but once it kicks in then feel the boost rush. I prefer the lag - makes for an interesting time on the straights at places like Coombe, Donny and Snetterton - cars dont know whats hit them when you just go flying past

Having had the 20g previously and mapped on race fuel you cannot compare at all - the 20g is much smaller and far less powerful - depends what you want. You pay more for a more powerful Turbo. The 321T is more laggy than the 20g on a 2litre - quite a bit so

You'd probably be looking at a 321T on an engine you've gone Internal on whereas the 20g is an ideal compliment on a std (400bhp is standard to me) sti where you only want say 370-400bhp tops

Whats the difference between the 321S and 321T (is it the exhaust housing size?)

I don't think you can compare a 321T to a 20g as said above.

However comparing a 321H to a 20g is far more interesting, especially if you have a 16g waiting to be converted... is a £1300 321H value over a converted 20g costing £550?

ive got a T on my 2ltr, runs at just over 420bhp on road fuel !!!

yer there is a bit of lag then then "bloody hell" any distance someone has made on u in that second you waited for boost is gone in a blink, while you woooossshhh past um!

Steve,

You had an earlier version of the turbo (S?) which whilst giving good power, was much laggier than the H, & T.

With regard to fitting, the MD321 series do fit in the standard location, using the standard fit up, & down pipes, but due to the increased size of the compressor housing, there's a small redundant lug that needs removing from the engine bell housing, which only takes a few minutes to do.

As for how well they work, I think the owners give the best descriptions.


Mark.

Your right- it took a minute or so to get rid of the metal in the way

Re earlier discussions - my memories going.......

If the T is less laggy then this is an obvious choice for most - as you have the potential later on if you want to run more boost - really then is a no-brainer

T would then be a nice compromise for someone on their way to decent power (over 400bhp) which the 20g struggles to achieve on road fuel

About 4 or 5 months ago there was a great discussion on the 20g verses...MD series with lots of facts etc.
Engine Ancilaries iirc.

For the money, the 20g is still here, but for the 'best' it has to be the expensive MD. 2 for sale already secondhand!

The search function though is near on useless since it was changed over a year ago - now I can understand why people repost as trying to do a search on a previous post can be a waste of time

I'll have another look for that Thread - I'm sure it was more than 4-5 months ago

lag ? what lag :D











oh , i've got a 2.5 ;)

awesome turbo , instant kick on an ej257 .
spools alot faster than a vf34 on a 2.0 litre (old set-up)

Might as well post this again:

http://www.zen16541.zen.co.uk/sti_rr_26mar07.jpg

Second line is torque, not boost, but follows the boost curve pretty well.


MD321H on a standard 02 STI 2 litre. Only running 1.4 bar boost though, hence the relatively low figures. It's running 1.75 bar boost now, but I've not been able to get it on a rolling road since the new boost controller was added.


M