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Discussion Starter #1
I am want to hear some thoughts on single vs twin turbo. Alot of people in the beginning said it wasnt possible to put a single on the z because the piping would be extremely difficult. Well turbonetics has proven them wrong and now its time for the official debate.

My thoughts:

The arguement i hear alot is that twins have less lag. Though this may be the case, our motor has more than enough power in the sub 3000rpm range to kill traction anyways. I have heard from numerous sources with greddy kits that 1st and 2nd gear are pretty much a joke, so maybe lag would be a GOOD thing for the Z. Lag was always spoken of in a bad way with reference to supras which couldnt launch and needed to spool to 6k rpms for any power. People fail to see that we dont have that problem..

thoughts?
 

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My friend told me I should get a single and with turbonetics bringing one out I am definitly going to be researching it. For some reason I have always wanted to just get a single but I thought it wasn't possible to put one on for reasons I never could understand. So good for turbonetics to prove everyone wrong. Hopefully it will do as well as the twins do.
 

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I think that a single turbo would be able to provide more power if it was an extreme engine build as was seen on an inline 6 engine(the supra and R3* Skylines). But with a V engine like the VQ35, now you have exhaust gases coming out in equal parts from both sides of the engine not just all together at once with an inline engine.

So now it would seem like a better setup to have two turbos providing the same airflow evenly, one from each side, then to have longer piping on one side of the engine to re-route the the exhaust flow around the engine to the single turbo. Granted this setup might prove that it really doesn't matter that you have longer piping on one side of the engine because it all meets up together before going into the turbo. But now you might encounter a situation where you are having turbulence buildup with the one side that has longer piping and this could potentially create a pulsation with exhaust flow going into the turbo. What does this mean, well if you are running the engine at high RPM, you might find that the single turbo is not operating smoothly, or it does operate smoothly but it is now not operating at its full potential, i.e. turbulence buildup. Where as two turbos will always operate smoothly because of the even piping. Where is the one setup better than the other and at what RPM or HP is a good question, but I couldn't tell you, that will come from experience and trial and error.

Now, please keep in mind that this is just speculation, but it is also a possibility.

The other question to ask about which one is better is to understand how you want to handle the difference in low lag time for the twin turbo setup as compared to the high lag time of the single turbo.

If you are looking to build an engine within the 400-600RWHP range, then the single might have the advantage with top end, but the twin turbo setup will accelerate slightly faster. Will you notice the difference, probably not.
 

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The turbo you go with will depend on Motor type, driving style and price.

A twin turbo whether it be parallel or sequential will reduce lag times by shortening the piping or staging the turbo activation as with sequintial. Twins are also known for a smoother throttle response and a little flatter power band.
the downside of this is the additional complexity of the design which will increase the chance for mechanical failure and the increase costs in manufacturing and installation.

A single turbo can provide the same overall power numbers but with a bit more lag and they can be handful when all that power comes on rapidly.

For my money if I was going to buy a supercharger based on price I would by the Turbonetics single. but if cost was no object I would be looking at APS or maybe a custom jobber.
 

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I'm pro TT. You can compensate for less CFM with one smaller and quicker spooling turbo by adding a second the same size. If I wanted to go for super hp, I'd just go with dual GT35's possibly even use a 45 compressor wheel, etc. Still spool faster than a single T. I'm against using nitrous, which of course would be a good trick to give a huge single snail setup better spool and down low grunt. I dont like the longetivity of the motor with n2o, atleast I could squeeze out a few more miles with a less severe setup using TT's.
 

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Originally posted by toykilla@Sep 28 2004, 07:36 AM
I

My thoughts:

The arguement i hear alot is that twins have less lag. Though this may be the case, our motor has more than enough power in the sub 3000rpm range to kill traction anyways. I have heard from numerous sources with greddy kits that 1st and 2nd gear are pretty much a joke, so maybe lag would be a GOOD thing for the Z. Lag was always spoken of in a bad way with reference to supras which couldnt launch and needed to spool to 6k rpms for any power. People fail to see that we dont have that problem..

thoughts?

I think you are confusing "lag" with "boost threshold."

Boost threshold= min rpm you can achieve max psi.

turbo lag= amount of time it takes to achieve your target psi, once you are cruising above the boost threshold at high vacuum and go WOT.

Both are important. Personally I want the boost threshold low enough that when I shift at redline I am still above my boost threshold. I want the most responsive turbo (least laggy) that can most efficiently maintain my target psi without falling off in the upper rev ranges.

Clear as mud?
 

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Discussion Starter #7
I understand what you are saying.. I think maybe in my case.. i would like to be able to stay out of boost during daily driving, but when i want the power its there..
 

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twins are easier to package, you can make awesome power with two small frame turbos, where to achieve the same power you would need a larger frame single....this is speaking strictly from a packaging standpoint.

single turbos have been known to be more efficient...but for street car purposes....silly power that a huge single can make...could be done with two small frame twins.

longevity wise...without a cross over to go from bank to bank...two turbos are better.

for a two bank setup, where a cross over needs to be used....single turbos dont really provide a great packaging for long term use, mainly because of the constant expansion and contraction of the tubing.

cast twin manifolds for twins will hold up better than a stainless manifold setup with a cross over.

im not a 350 person...but this is pretty much a general rule of thumb
 

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I believe I’m in the same boat and carrying the same theories as Josh is. I am more than pleased with my down low power and think much more down low is only going to make the car slower if you are constantly on the ragged edge through the corners because your peaky torque curve wants to snap the rubber from underneath you. The added delicacy would definitely require a lot more skill to be as fast as something more manageable with less low end power.

Keep in mind that when people compare to lagging single turbo supras and what not they are referring to a 3 liter engine with low compression pistons (read: very low torque downlow) that have massive turbos capable of 25+psi usually. So, we know that the car should perform on par with a stock Z at levels before boost is created, assuming that the back pressure changes don’t affect things much. MIAPLAYA, who road with Turbonetics in their single turbo car, has stated that
they were in boost at 3k rpm and were generating max boost by 4k rpm. I’m not sure how your guys are driving, but I’m usually shifting at about 3500 in daily driving situations so that is just fine for me. I could stand for it to be a little higher even, since it would keep stress off the engine in daily routines and add longevity.

On a side note, both my twin turbos 300’s (3liter, 8.5:1 pistons) didn’t hit boost until about 3300 rpm. Another factor to consider, if you don’t like the turbine configuration on the kit or have a motor build/failure or whatever……or if you just want to experiment and trade big end for spool time…the turbo itself can be removed in 20 minutes.

You also get to keep your front crash support, which is a biggie for me.
 

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For a high end street setup with lowered CR (~8.5:1) I consider a lower boost threshold far more rewarding. In this case some of the low end NA TQ is lost and can be recovered far more adequately useing preperly sized twins. Hence why my plans are APS on a 8.5 CR long block. Block is built , awaiting the APS kit mods for G35. And additionally , though mostly a Cali concern , the single on VQ35 has no chance in **** of ever meeting CARB for many many tecnical reasons. At least a preperly designed twin does have a fighting chance. If any one beleives the TN single on the VQ could ever pass CARB (not that it is being pursued) , they are delusioned.
 

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not a big concern in Texas as you can always find someone to hook you up and pay under the table for a sticker. But I agree, if carb certs are a concern, I wouldn't even blink at the t-netics kit.
 

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With the exception of g3po have any of you driven a non-factory turbo vehicle? Seriously, IMHO you shouldn't rely on high-boost threshold to keep the car controllable as the opposite will result. Power is (an always has been) controlled by the throttle!!! If you don't want full boost don't go WOT (wide-open throttle), boost (in a turbo car) is dependant on throttle position and engine load.

I rather have boost come on low and progressively then come on in the mid-range and hit like hammer to back of my head.

QUOTE
I am more than pleased with my down low power and think much more down low is only going to make the car slower if you are constantly on the ragged edge through the corners because your peaky torque curve wants to snap the rubber from underneath you. The added delicacy would definitely require a lot more skill to be as fast as something more manageable with less low end power
Whatever makes you happy, but more power has NOTHING to do with the speed you can carry in the corner. It will make you faster out of the corner and down the straight! High boost threshold is indicative of a peaky powerband not the opposite!!! You guys scare me...
 

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A little info about the APS system. If you want a ramped, flat, spiked etc. etc.., is is readily poassible to tune the Unichip to map whatever boost profile you want. He piggyback controll the boost controller as well as A/F and Timing. So if a huge flat and early TQ curve "scares" someone it can be shaped. Of course access to the Unichip Software is only provided to APS / Unichip reps. Personally I prefer as early and as flat as possible, as mentioned let your throttle be the moderator. With a high boost threshold and late TQ curve , you really have no option other than a NOS shot.
 

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Originally posted by toykilla@Sep 28 2004, 07:36 AM
I am want to hear some thoughts on single vs twin turbo. Alot of people in the beginning said it wasnt possible to put a single on the z because the piping would be extremely difficult. Well turbonetics has proven them wrong and now its time for the official debate.


HI Guys,

It's very possible to package a single turbo (in fact APS prototyped and tested a single Garret ball bearing turbo on the Z over a year ago) as with all performance products this single turbo approach has positives and negative aspects.

I have listed below just a few of the pros and cons for the single turbo approach, there are more of each than I have listed though these are the obvious points to consider.

POSITIVES - Single Turbo System

1) Less capitol required for tooling

2) Cheaper production cost

3) Lower MSRP

4) Quicker install time

Negatives - Single Turbo Sustem

1) won't ever meet CARB engine emission standards - Gain CARB EO

2) Maynot meet local state emission tests

3) Higher under hood temperature - air temperature and additional radiant heat

4) Much slower to spool than Twin Turbo approach

5) Much lower Torque and power (under 4000 rpm) than any Twin Turbo system that APS has tested.

That's not to say that this single turbo approach does not have a real place in the FI market as it obviously does, it's just that the single turbo will never match the overall performance of a well designed Twin Turbo system.

I've now driven and tested I believe just about every form of FI for the 350 Z and I believe that the single turbo has similar road performance to that of a large centrifugal Supercharger system.

This is where APS would target a single turbo product (an APS single turbo system if ever produced) in terms of MSRP and performance and the single turbo system would be a really strong competitor to the many centrifugal blower systems.

Ultimately a well designed Intercooled Twin Turbo System will out perform a Large single turbo in every facet of measurable performance, stronger low rpm response, better mid range torque, greater high rpm power,quicker partial low rpm throttle response, more efficient fuel consumption and most importantly on the road and track where it all counts..............all be it at a higher starting cost though the rewards of the Twin Turbo approach will bring a huge smile to your face for a very long time


Peter

APS
 

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The only reason I would see to purchase a single turbo would be cost. If the street price for the Turbonetics single is around $4000, I would opt for that over an SC. But like Peter said, a single turbo on a V6 motor will never have the performance capabilities of any twin. Twins will always been more efficient in a "V" engine configuration, and singles usually work best in high HP "in-line" engine configurations. The turbos need to be as close as possible to the manfiolds...ie...attached to them for maximum exhuast scavenging..and efficiency. :) That is not possible with a single setup on our car.
 

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.....I degress
 

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Originally posted by MIAPLAYA@Oct 21 2004, 08:51 AM
.....I degress

A little more info what be helpful.............I could not find the meaning of the word degress in the oxford dictionary. :headshake:

Peter

APS
 

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I will interject here since i have been folowing this debate from other sights for years and most recently my350. I have owned several turbo vehicles in my past and getting ready to own a 350. My list:

'87 GN
'89 TA 20th anniv
'96 300Z TT
'93 Supra dumped the twins went for the single: sold needed a house.:angry:
'97 Mustang GT started out as Supercharged for 1yr hated it..went to single 62-1 turbo and never looked back.
Dad owns '87 930 Turbo and '97 911 TT and my old TA.


'87 Grand National 3.8 V6 Turbo traded for same motor as the GN a '89 20th anniv Trans am pearl white which still sits in my fathers garage(he offered a price that i could not refuse) with 48k on the odo. Now these cars performed very well with great straight line speed and they were both V6's. The TA with about 350 est. with minor blot ons would outrun my friends stillen stage 2 TT Z with around the same HP. now this is going back 10yrs or so.

Now I am little disturbed because people that are judging this kit have not had any wheel time on it. Me personally i love the way singles respond and that kick in the pants it gives at mid rpm feels like you are god when things get aggresive. Yes TT are have good linear power and and are very efficient in their range but in the higher rpm a single will produce more hp than the twins will, at least that was the case with my supra. As far as heat concerns, i think the TT would put out more under hood temps than a single, i mean 2 turbos vs. one.

I think the only true way to put this to rest is a some test from 0-60 (i know that the TT has this one) from 40-120mph and a good top end run..then maybe we can put this one away..
 

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Unfortuntaely, you are right...we are just specualting and discussing, since I think only one or two people have driven the Turbonetics single turbo car. I will tell you that your Supra definately has improved performance with the a single big turbo mounted up to the manifold, vs. twins...since is a inline 6. I still feel, and this is just basic turbo common knowledge stuff....is the all things being equal, you'll get better performance and efficiency bolting a turbo directly up to the exhuast manifold.
 

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Gq..
you are correct, it i did have improved performance on the top end sucked on the low. suffered from being a big single and .80+ AR.

Well i never had problems with my other cars especially with 3 V motors i had in the past. maybe the were they not as efficient as the twins because i never bothered looking at compressor maps but they got the job done and in a rather quick way.

I mean honestly how much do we really care about efficiency?? Honestly if a vendor puts out a product that says for ie. Brand Z has an output of 500hp max now there is brand X which has a different config does the same thing but has a output of 600hp max..how many of us are actually going to say, well i will go with brand Z because it is more efficient. No, must of us will say **** i want power.. Personally i dont care how airflow gets to the intake, as long as it is lots of it and safe it should not be a problem.

I think the efficiency you are all talking about is the maybe spool time. other than that this is the way i see it:
TT- compressed air leaves from both turbines into the IC from there up to the intake..
T- same concept as the TT except only one turbo, now where is this that inefficient? except for the distance that it has to travel to join the other manifold..and once you are under boost you wont feel any lag just all power..
 
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