https://mustangforums.com/forum/4-6l...ut-turbos.html

 

The 76mm turbo on a built 2v with race ported heads and 9:1 compression isnt too much i'd say. His heads were running right around the same amount of cfm as some cobra heads, and a 76mm is a good sized turbo for a stock 03 cobra setup, or else hellion wouldnt have paired that setup. So i feel like a fully built MMR 2v with a single 76mm turbo is just about right. Needs different cams though...

Now in reference to the 50mm turbos being just about right, I just dont get how twins are going to do you better with spooling. They are smaller turbos, but they are being spooled by 4 cylinders each when you think about it. Its like a honda civic running a 2.3L motor trying to spool a 50mm turbo, which is still not ideal really. Running a single 76 is like running twin 38mm turbos really, unless im missing something here. Is running two smaller turbos off of 4 cylinders each different than running one larger turbo off of all 8 cylinders??? If its the same deal, then the single in all reality should spool quicker than the twins in this case.

Now about the whole supercharger situation and the track references...you have to definitely be more tactful leaving a corner with a twin screw than with other power adders. Instant boost will just suck for a track car, let alone the heat soak. But i can see how centris would work well on the track because they dont heat soak as bad as a twin screw and you have better cooling and such, but personally i think the best road course setup is N/A honestly. No worries about heat soak or boost hitting or anything. But you are right about the apex statement. You want to stay out of power before and then when the apex hits you want to start laying into the throttle as much as possible while maintaining traction to shoot you out of the corner.

And thank you for not bashing and civilly discussing the topic, rather than jump down my throat about it. Much respect man.

 

well we are all a bunch of know it alls...have to use tact! lol. and honestly i dont know why it makes a difference, youd have to ask a turbo guy, i love them but dont quite understand everything about them. but i do think the twin 50s spool faster than the 76....maybe im wrong, altho your logic makes sense...

 

...

 

Yea, i looked through that and the link, but im still wondering about the whole deal with people saying twins spool faster, when in fact its taking 4 cylinders to spool a 50-61mm turbo, when you could be spooling 76mm worth of turbo with all 8 cylinders.

 

Usually with twin turbos they are smaller in A/R. Since their A/R is smaller this will allow the turbos to "seem" to spool "quicker". When people do single turbos they do not choose a small turbo. The norm is a 70 mm turbo. This allows them to have room to grow to 700, with a turbo that still falls within the 78% range, and they don't have to change out the turbo when time comes. Ex: my turbo will be a 70mm. Obviously I am leaving out some feasible power band but there will be more power from the 70mm in the upper RPMS. This will make for, what people refer to, a not so fun street car. Twin turbos are smaller in A/R, which spools the turbo faster as a whole over single because single usually have a higher A/R, thus using more power band.

 

So for my application, 2 smaller turbos which would provide more of a linear power curve, is recommended? The car see's about 20k miles a year as a DD and see's soloII's every now and then.

 

basically, 70mm plus is too big for streatable funness...lol it will go like stink, and if you set it up right you may even make good times at the track, but you do still have the lag to deal with. Moving back to the turbo thread, join us teej. on that subject i imagine those 50mm twins tap out at like 6k or so? where the 70mm would be still good? or am i thinking of this wrong...i have to acctually do some calcs with the stuff you gave us.

 

As far as a graph go, how will one look as apposed to the other? the 70mm will have an exponential spike whereas the twin 50's will be more linear, or will they both be pretty exponential with the 50's being closer to linear?

 

^Not necessarily. The 70mm turbo would be perfect for street funness, as long as it doesnt have a huge A/R, if i understand it right. Turbos come in all different sizes because of the different power needs that people are gonna use them for.

To Aereon: The twin 50mm turbos wont be linear, but they will be closer to linear than a single 70mm i'd say from what ive been reading lately. The actual linearness of the graph will all depend on how quickly the turbo(s) spool. If it spools hard later in the rpm band youre going to have a more non-linear power curve. If the turbo(s) spool sooner in the rpm band, you'll get a more linear curve because you wont see the spool on the graph because they will instantly spool. If that makes sense...