Dumb Question - I searched

[Silver98Maro]

ok so obviously not every turbo works on the L36. but what is the difference between 7 Psi from a T3 and 7 Psi from a T4. I realize that the T3 is generally used on I-4's and not something this size, but what other factor determines which turbos will work.

[Shane]

every turbo can be made to fit our car with the right fabrication.

[ReodDai]

Put it this way.. the different turbo's basically come down to what kind of turbine and compresser blade is in them. The rest is just a housing (yes I know water cooling and oil cooling, internal wastegates ect ect but for explaining this is the simplest). It takes certain amount of air to push the blades, the larger the turbine the more exhaust(pressure, not how big you make the pipe) needed to make it spin... thats roughly why a large turbo doesn't begin to produce significant boost untill higher rpms. T3 and T4 are very similar so the difference wouldn't be entirely that much, if I remember correctly the same amount of boost would roughly product the same horsepower but at a different part of the power curve. For example, small turbo produces boost at low rpms, but max's out before you get to 4000 rpm. On the other extreme a large turbo doesn't begin to start to produce boost untill 5000 rpm but doesn't reach full boost before you hit your max rpms. This is the main reasons people say they design a turbo to fit a car. You can technically fit almost any turbo in a car as long as you have room. But only some will be usefull for what your going to use it for (ex: street, autocross, drag) If I'm wrong... ask tiago lol

[Riles]

I'm not sure about what Reodai said, but the differences will be in efficiency. I havent done the math on these two in particular, but given the airflow and boost (7 psi), each turbo will produce different amounts of heat.

There are efficiency charts on turbonetics.com- if you read them, you can find 7 psi and, if you know your airflow, you can find out how efficient each one is.

[Silver98Maro]

efficienty sure, but from what I am understanding from ReodDai the ideal turbo for the L36 is one that fits its powerband, which is 4000-6000rpm's (correct me if i am wrong). thanks for the replies, i usually don't get any when i post, much less so quickly. I'm guessing that the turbo Tiago selected for his kit (T3-4 Hybrid?) is one that fits the powerband the best?

[nocutt]

<blockquote>quote:</font><hr>Originally posted by Silver98Maro:
efficienty sure, but from what I am understanding from ReodDai the ideal turbo for the L36 is one that fits its powerband, which is 4000-6000rpm's (correct me if i am wrong). thanks for the replies, i usually don't get any when i post, much less so quickly. I'm guessing that the turbo Tiago selected for his kit (T3-4 Hybrid?) is one that fits the powerband the best?<hr></blockquote>

Actually it is more complicated but I agree with everyone on this thread...
Generally, the bigger the turbo the slower it spins because of the inertia it has to overcome due to its size...generally! And vice versa with a smaller unit...The problem also lies typically on the end user...what you intend to do with the car...Street/strictly, street/less track, inbetween then all out track (drag) then there is road racing...etc The l36 makes good power from idle all the way to 5800 stock, all this doesn't matter with a turbo generally speaking!...however with a smaller unit, you will likely kick it out of it's efficiency island before even making it to 5K..now smaller is relative, because some ppl might want this sort of character...not to say there isn't any power at higher RPMs you just feel NOTICEABLE drop in power...for someone who road races higher RPMs aren't really necessary so a small turbo will work fine especially with an A4...Yep even trannies create another variable...ultimately a compromise will always be made hence a lot of folks use a t3/T4 hybrid which is actually A best of both worlds and this family of turbos can always be upgraded to flow enough CFM for 500-550hp ;)

[Silver98Maro]

I knew nothing about turbos a week ago. Slowly learning more....I think I will get a book

I originally thought that a sequential twin turbo would be the best for the L36, keeping the sum of the Psi no higher than 7. One would get the perfect balance, the quick spool of the smaller one with the higher RPM of the larger.

Not only would it be more difficult to do with piping and installation, but it's not even cost effective.

nocutt, thanks for leading me to the question in my head that I never asked....a turbo that works very well with the 3.8. Doing searches, I found people using T3's and T4's, the T3/T4, T-25, various other types.

I know that what I posted was a general case that had a broad range of answers but I think that all of you guys have helped me considerably.

[ReodDai]

Do not curse the f-body with sequential twin turbos.. please.. just don't do it. I have yet to see a sequential design that isn't flawed that didn't cost a vital organ to have fabricated. Plus they take alot of upkeep, and have very large problems with boost creep. Also the transition point would be VERY dangerous in an f-body. Our cars already have a tendancy to have the tires break loose and have significant body roll (stock atleast). Btw, the transition point is the point when you switch from primary to secondary turbo. Using a rx-7 as an example their stock boost pattern looks something like 10-8-10. If you get that second turbo kicking in on a slight curve of the road you could send yourself into a tail spin (don't believe me ask a fd3 owner).

Additional Notes: Sequential Turbos do not run at the same time.. ever.. when one isn't working it maintains an idle speed that is all. Therefore there is no "sum" of psi. The primary turbo kicks in at around 3k (roughly) and lasts till 4-4.5 then the secondary kicks in, and the primary shuts down till redline (this is just an example if you would like I can look up the exact numbers).

[ September 26, 2003: Message edited by: ReodDai ]</p>

[Silver98Maro]

<blockquote>quote:</font><hr> Do not curse the f-body with sequential twin turbos.. please.. just don't do it. <hr></blockquote>
- ReodDai

<blockquote>quote:</font><hr> I originally thought that a sequential twin turbo would be the best for the L36, keeping the sum of the Psi no higher than 7. One would get the perfect balance, the quick spool of the smaller one with the higher RPM of the larger.

Not only would it be more difficult to do with piping and installation, but it's not even cost effective.
<hr></blockquote>
- Silver98Maro

;)

Mucho Gracias on the Info though!

[ September 26, 2003: Message edited by: Silver98Maro ]

[ September 26, 2003: Message edited by: Silver98Maro ]</p>

[Tiago]

<blockquote>quote:</font><hr>Originally posted by nocutt:


Actually it is more complicated but I agree with everyone on this thread...
Generally, the bigger the turbo the slower it spins because of the inertia it has to overcome due to its size...generally! And vice versa with a smaller unit...The problem also lies typically on the end user...what you intend to do with the car...Street/strictly, street/less track, inbetween then all out track (drag) then there is road racing...etc The l36 makes good power from idle all the way to 5800 stock, all this doesn't matter with a turbo generally speaking!...however with a smaller unit, you will likely kick it out of it's efficiency island before even making it to 5K..now smaller is relative, because some ppl might want this sort of character...not to say there isn't any power at higher RPMs you just feel NOTICEABLE drop in power...for someone who road races higher RPMs aren't really necessary so a small turbo will work fine especially with an A4...Yep even trannies create another variable...ultimately a compromise will always be made hence a lot of folks use a t3/T4 hybrid which is actually A best of both worlds and this family of turbos can always be upgraded to flow enough CFM for 500-550hp ;) <hr></blockquote>


the hybrid we used on the prototype made positive manifold pressure at 1500 rpm :eek: and hit full boost by 2500 rpm, kept pulling hard till redline. I think it worked out great.

Tiago

[ReodDai]

It hit full boost at 2500? Hmmm.. temps should be scorching up at redline, but hell if it can take it awesome job =)

[snatch]

Hey I dont want to steel the thread but I also have a dumb question and was to much of a pu$$y to post it. When I went and got my car dynoed we got a group purchase cause a bunch of ricers went, and I noticed that the ones running nitrous or a turbo would just smoke you out of the shop with the unburnt fossil fuel that flew out of their exhaust.
I know that that is running rich but I didnt see any of the neon srt-4's doing that and I havent noticed any turboed porche's doing it either, I was just wondering when someone installs this turbo kit if their car is going to smoke like crazy? Is their something that can be done to remedy this?
Again I'm sorry for posting this question inside of someone else's question and if you feel I should open a new thread I will.
Thanks Shane

[ September 26, 2003: Message edited by: snatch ]</p>

[nocutt]

The general rule of thumb is to ALWAYS run fat before a dyno tune...it helps in many ways but you aren't at optimal power...
I have never seen a dyno for a porshe but I have seen that two for the SRT-4. They run rich from the factory and Dodge seem to be placing the SRT-4 numbers on the conservative side...
SO you know there is a big difference between big rich and rich...lol!

Tiago...
Very interesting, we have dynoed two 3800 turbos and only the 3800 with the t3 made full boost at 2500RPM and took a nose dive by about 4K...this was with a 5spd...

[mattsv6]

what model t3 was it? s60? what compressor wheel and housings? that might be the problem that casue youu too blow hot air right there. and s60 would be nice on a stock motor with about 10psi. but it would be inefficient after that. this is why we runnin t4series

[Camarorulz]

Tiago, that's impressive if it achieves full boost at 2500 and runs strong until redline... I thought it wouldn't make full boost with a T4 until at least 3000+. Wow, with my converter I could be above full boost out of the hole... [img]graemlins/omg.gif[/img]

[ September 29, 2003: Message edited by: Camarorulz ]</p>