Twin turbo M20, is it worth it?

[Coyote_ar]

Just that, being curious.

[fowler]

well with all the effort to make it twin turbo in answer no. a single turbo conversion is more than adequate.
if you are set on twin turbo you can alswyas use the M50B25 and twin turbo
On a single turbo set-up on a M20B25(low comp ) Post 88 engine will take a roughly 1Bar of boost on stock internals (engine condition providing)
it would be easily obtainable to get 350 Bhp out of a FI M20 B25 on a single turbo set-up.
if you wish to take it further. A M20 B27 low comp acn be built to make near 500hp quite easily.

[Gunni]

Let´s just say with either you can reach the M20 limit of 1100hp.

But what is the goal of this engine Coyote_ar?? What hp and driving charecteristics.

[Coyote_ar]

fowler, i think the biggest advantage of a twin turbo setup its not the power gains, but the low end torque and the reduced turbo lag. you can achieve any crazy hp with a bigger turbo and stronger internals. but it wont be a nice car to drive, only for drag racing.

gunni, at this moment im not planning un building such engine, just wondering.

but say this engine would be intended for daily driver + track day. 300-400hp. how does a single turbo M20 perform in this kind of use? is it a nice engine, or is it a bit annoying? will the twin turbo setup be way more flexible and smooth running?

[fowler]

Its good setup on single because if you use the right turbo there is releatively no lag i have HX35 extrenal wastegated on a M20B27 low comp with TD crank and all the bits. and boost was starting to come in by 2800rpm and full boost by 3500rpm. this is a relative big turbo conversion.
If you want that sort of horse power you have described and the delivery you want. you should supercharge it for the low end grunt ideal for daily driver and track car
One of A-Tech (01959534718) bolt on M20B25 supercharger kits (engine management required) will do the job perfectly.
regards
Ben

[Turbo-Brown]

Personally don't think you gain anything with a twin parallel turbo setup.

Yes the turbos are smaller, but they each only get half the exhaust gas to drive them so lag isn't much different.

My twin turbo setup (using skyline turbos) was making boost by about 2500rpm which ain't much different to Fowlers HX35 by the sounds of it.

Now if you could make a twin sequential system work........

[fuzzy]

boost starting to come in at 2800rpm is in my opinion quit laggy. a smaller housing turbo will boost up quicker to feed a big turbo so twin sequential turbos would be a good set up in 6 pot bmws.
i had a .63 housing turbo on my engine ,boost came in at 2500rpm, dropped to a .48 housing and boost now comes in at 1400rpm which makes it a far more usuable car.

[jaistanley]

Now now...

Lets not go all motoring journalist and mix up lag with boost threshold here.

[Gunni]

boost starting to come in at 2800rpm is in my opinion quit laggy. a smaller housing turbo will boost up quicker to feed a big turbo so twin sequential turbos would be a good set up in 6 pot bmws.
i had a .63 housing turbo on my engine ,boost came in at 2500rpm, dropped to a .48 housing and boost now comes in at 1400rpm which makes it a far more usuable car.

it´s real simple.
quick boost and low threshold <=> very high power and good high end VE and safety.

Only a sequential turbo setup can do both.
low end + high end + good VE and safety everywhere.