I have been following the evo 5 thread. You cant really tell anything from video. You cant see the tach, the speedo doesnt work either. And there is no dyno posted. He did say he was making 480tq at 4000rpm like that was impressive. I have seen a local FP black make 570wtq at 4100 rpm on a stock 2.0. The whole purpose of a twin setup is to gain a broader power band than what can be achieved with a single setup. The only setup that worked from very low rpm and made stupid flat torque was the norris setup. twin turbos arent capable of such a feat. unless is setup as sequential. but most are onto the compound turbos. they give big turbos better spool but they fall short in the low rpm below 4000. they also choke up top more because most the exhaust still has to go through smaller turbo which creates high back pressures

 

And this is how suspect norris did it. Use a small super charger that makes boost right off idle. and then shut the charger off with a/c style clutch, and bypass air around it. then at higher rpm have at it with oversize turbo that is unrestricted by the first.

I dont think the evo 5 is bypassing the supercharger. you can here it the whole time. so the torque curve will fall at higher rpms due to inefficiency of surpercharger in the way.

If some one could just share what supercharger setup was used I would consider building one of these. It may actually be from the 1.4 engine. There is a toyota roots charger being sold regularly on e-bay right now. they come with clutch and bypass valve. but the engine was a 2.4. the charger looks to be on the large side for the project. it came on a toyota previa. I cant find a dyno curve of the previa anywhere. but it may have impressive torque at 2000 rpm. then shuts off charger at cruise speeds.

 

Amen.

239 bhp = 178kw

178kw = 607,523 BTU

I dont have the formula to convert that to specific heating (in this case melting) terms, but I seem to recall someone on NASIOC posted this in regard to the Subaru tranny and it was something like 420*F in short order, but the thermal loss wouldnt stop right away. It would get hot enough to melt the transmission as I recall.

 

Only the exhaust required to maintain the set boost for the small turbo goes through its turbine, the rest is wastegated around it, in my case by two V44s. Have you ever measured back pressure on a compound system? Obviously not.

 

so your saying you think a 42r on a twin compound turbo will have less backpressure than a VW design twin charge using a 42r for the turbo? I hope not. Your setup has not bested a good hta86 setup. So if you want to come in saying how great your powerband is I wont be listening. you need to learn how to read a dyno graph..

 

Post back pressure data logs and we'll compare. I wouldn't be surprised if a SC based system had slightly lower drive pressure at all. I would expect drive pressure to be the same as the turbo would have in a single turbo setup, which isn't much better than what I see BTW. My point is simply that you have no data for comparison, all you bring to the table are dyno graphs you found on the internets. I at least have data on a compound turbo setup. You can't make blanket statements about compound turbo back pressure when you havn't collected any data on one. All we need is data on the other type of setup and we can do a real comparison. Until then you're not going to convince me that compound turbo setups don't work well.

I fixed it. You're comparing apples to oranges. I'm running through an auto tranny and 7500 rpm converter on a RWD beam axle platform. I need to make at least 100-125 more crank hp than a manual trans car to get the same whp. An HTA86 wouldn't even spool on my setup and would run 15s, it's useless to me. You have to compare the single turbo to compound turbo on my car only, not completely different setups that suit your position. Stick to comparing SC/turbo to turbo/turbo setups, you're moderately better at that.

I can't even start a dyno pull below 7500 rpm because of my converter, good luck comparing that dyno graph to someone else's.

 

Kevin, all your babel completely useless to me. I am interested in the twin charge setups that make a nice road car. When you have that built I will listen to your experience on the subject. I know your setup works very well for its intended purpose. Its just not at all what i am after. The only dyno graphs posted of compound turbo setups that are worth looking at are from CPR. and they clearly are also not what I am after. no power below 4000rpm doesnt work for me. I am looking for the broad (starting at low rpms) like the VW 1.4 produces, or the Porsche twin turbos, or the best I have seen hands down the Norris project car.

 

i dont have much to input on this but i saw something about a previa s/c and i have to say i have one and it is fun as hell to drive in the rain. Def enough torque to get sideways but it only make 3 or 4 psi if i remember correctly, but i dont know where its peak efficieny is

 

Well, that's a little better. I'm glad we had this conversation.

I understand that compound turbos are not for everyone. When you build whatever it is that gives you what you want, be sure to post the data, I'm always interested in hearing more about these unusual setups.

 

I have seen the previa chargers. They are correct design for the task. They have clutch to disengage the unit after boost is achieved. They have the baypass, but the bypass valve would be far too small for our purpose. The 2.4 previa engine achieves 200tq at 3500rpm with 6psi. Not sure if it would be correct size for project. It may be just right with smaller drive pulley. The norris car made 300tq just over 2500rpm on a 2.4.

The dyno graph posted of the norris car was also not the finished tune. it made 1100 hp with .2 bar more boost!

 

Kevin, i am not sure the compound setup incapable of giving me what I want. Of all the setups i can find they all using too large primary turbo (first to see exhaust) . It may give the results I am after with something like a 14b/35r setup. I built a 2.4 years ago that was built for a 35r. It was run with a 14b on it for a month. I may be one of the few on the planet that has felt a 4g63 with that much low end. But i tell you what. That car was an absolute blast to 5000rpm. boost started at 1800. had 21psi by 2100rpm.

The superchargers setups are better design in a sense the charger can step out of flow path after boosting. But far more complex. A twin turbo setup sounds much more simple to me and ultimately more reliable. as we know turbos at 20psi live forever.

 

be careful with the toyota chargers, i am *guessing* its a SC14, not the most efficient things out there, plus when temps get hot the teflon on the rotors melt, you lose sealing and boost.

 

I've been in a DSM with an EVO3 16g and a 2.4 liter, and the low end was insane. In a DSM though it rarely results in anything more than scattered drivetrain parts. A 14b and a 35R are a reasonable match.

The small turbo in a compound setup steps out of the way too, by way of wastegating, but there is still the drive pressure associated with maintaining it's (relatively low) PR, as we discussed above. If the SC drops its parasitic drag when it's bypassed it should be a little better overall, but the data will show whether or not it's worth it. Both of my turbos "feel" like they are making 15 psi (2:1) at 45 psi, they both look brand new despite hammering on them constantly (and with no BOV).

The 14b/35R combo would be nice to see some numbers on. Most people wouldn't bother since they can live with a 35R sized turbo on its own, you'd probably be the only one willing to try it. I need back pressure numbers on at least one other setup that's a good bit different in size than mine to start to determine what the trends are as you change turbo sizes. I may swap to a .63 housing on my 50 trim to spool up a little quicker for competition, but the cost to benefit ratio is too high. It would be one more data point though, even if it's not much of a difference. I'm currently a touch above 1:1 (~47 psi drive pressure at 45 psi manifold pressure, through a 4" FMIC) with crossover happening at or above 8000 rpm, which isn't bad for a turbo that "spools" at 4000 rpm. I would expect the 14b setup to go vertical at 3000 rpm in my setup, but on a 5 speed where you can load it better it should do even better than that.

Just for fun, a compound Pocharger setup recently went 4.008 in the eighth mile too BTW, for another type of setup that's doing well. Gets on the converter instantly...

 

I had a 14B on my 2.4L Talon as well for a while and man it was just like a Mustang! All kinds of tq and no top end. Mine had an issue with the WG sticking open causing a complete loss of boost occasionally but it was fun. Ran a 12.6@110 with a whopping 12psi by 6krpm. I didnt realize the boost was falling down so low so fast and my SC61 had a 16psi wg so I had between 5 and 16psi running very rich with retarded timing to spool the bigger turbo. I wish I had tuned it a little better to maximise that setup. For S&G's I may slap it back on and see what she would do properly tuned. Can you say 330whp and 500tq? That would rock! I had a 7cm housing on my 14B though so it wasnt a stock turbo per se.

 

as already been said, they SC14 is off the 2.4 litre toyota engines. the SC12 is off the 1.6 4age.
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