My observations and opinions of current street/strip turbo LS trends.
08-11-2012, 12:26 AM
#1
FormerVendor
Thread Starter
My observations and opinions of current street/strip turbo LS trends. The following thoughts and rambling is directed towards what I see as the majority of the street/strip turbo LS crowd. As a disclaimer, the following is my -opinion- but it is backed by experience. Oh yeah, and I don't sugar coat things.
First off, the same with anything, a turbo LS needs to be looked at as an entire, matched combination. Set your goals first and then decide on components that will allow you to reach those goals.
That being said, big compressor wheels and tiny turbines seem to be all the rage these days. Guess it makes for an affordable turbo. It also makes for sub-par performance.
If you've decided that you absolutely must use a 76mm compressor and a 12mm turbine
, really don't even bother with a "what cam should I use" thread because if you have money for a cam that will do absolutely nothing for you, it should be spent towards a turbo that is actually capable of efficiently making power.
Why does your car nose over at 5k? Chances are your turbo belongs in the dumpster or you have way too big of an engine for your current turbo. Want to make 950rwhp and 7000rpm with a PT7675? Run a 5.3. Want to spend more money on a 408 and max out the same turbo at 775rwhp and 5200rpm? Probably not, but people do it.
Not sure why but it seems many people shy away from twin setups. Twins absolutely cannot be beat in terms of a fun street car. Even an undersized pair of twins that make nearly instant boost will still outshine most similarly capable singles up top. I don't like lag so I always run twins. And I'm not talking logged boost VS wot, I'm talking about having driven countless amount of turbo cars and knowing the difference in feel when you roll on the gas of a single or a small set of similarly capable twins. Transient response is what you feel in normal every day driving and you get it in spades with a good twin setup.
Rear mount? Sure they can be fast at the strip as you have time to get the things online while you're bumping it in. As for a fun driving combination on the street? None that I've driven accomplish that. Wouldn't use it if it was given to me. (refer to, I don't like lag so I run twins/etc/etc)
Back to the cam thing. I'll use the cams we have available as examples because well, why not. I designed them and tuned them over the years so at least I can speak about them with experience.
TUO-216/216 114lsa. I would plan on bigger if I planned on over 700rwhp.
TU1-225/225 113lsa. I may consider a bigger cam if 950rwhp wasn't enough.
TU2-236/236 112.5lsa. If you have a combo capable of 1200rwhp and 7800rpm than this cam will work great.
Guess the point I'm trying to make on cams is that I think 90% of people cheap out on their turbo then over-cam the hell out of it thinking it will somehow compensate when in reality all you did was soften up the bottom end and midrange for no gains up top.
So, in closing, if you're building or planning a build on a turbo LS and your goal is to not be disappointed, THE most important thing to buy is a good turbocharger or turbochargers. Second is valvesprings. If you cheaped out on the turbo so you could buy more cubes, a different intake manifold, a different cam, a set of heads, a throttle body, an electric water pump, or even a torque converter, you've made a poor decision.
Rant over, let the flames begin
First off, the same with anything, a turbo LS needs to be looked at as an entire, matched combination. Set your goals first and then decide on components that will allow you to reach those goals.
That being said, big compressor wheels and tiny turbines seem to be all the rage these days. Guess it makes for an affordable turbo. It also makes for sub-par performance.
If you've decided that you absolutely must use a 76mm compressor and a 12mm turbine
, really don't even bother with a "what cam should I use" thread because if you have money for a cam that will do absolutely nothing for you, it should be spent towards a turbo that is actually capable of efficiently making power. Why does your car nose over at 5k? Chances are your turbo belongs in the dumpster or you have way too big of an engine for your current turbo. Want to make 950rwhp and 7000rpm with a PT7675? Run a 5.3. Want to spend more money on a 408 and max out the same turbo at 775rwhp and 5200rpm? Probably not, but people do it.
Not sure why but it seems many people shy away from twin setups. Twins absolutely cannot be beat in terms of a fun street car. Even an undersized pair of twins that make nearly instant boost will still outshine most similarly capable singles up top. I don't like lag so I always run twins. And I'm not talking logged boost VS wot, I'm talking about having driven countless amount of turbo cars and knowing the difference in feel when you roll on the gas of a single or a small set of similarly capable twins. Transient response is what you feel in normal every day driving and you get it in spades with a good twin setup.
Rear mount? Sure they can be fast at the strip as you have time to get the things online while you're bumping it in. As for a fun driving combination on the street? None that I've driven accomplish that. Wouldn't use it if it was given to me. (refer to, I don't like lag so I run twins/etc/etc)
Back to the cam thing. I'll use the cams we have available as examples because well, why not. I designed them and tuned them over the years so at least I can speak about them with experience.
TUO-216/216 114lsa. I would plan on bigger if I planned on over 700rwhp.
TU1-225/225 113lsa. I may consider a bigger cam if 950rwhp wasn't enough.
TU2-236/236 112.5lsa. If you have a combo capable of 1200rwhp and 7800rpm than this cam will work great.
Guess the point I'm trying to make on cams is that I think 90% of people cheap out on their turbo then over-cam the hell out of it thinking it will somehow compensate when in reality all you did was soften up the bottom end and midrange for no gains up top.
So, in closing, if you're building or planning a build on a turbo LS and your goal is to not be disappointed, THE most important thing to buy is a good turbocharger or turbochargers. Second is valvesprings. If you cheaped out on the turbo so you could buy more cubes, a different intake manifold, a different cam, a set of heads, a throttle body, an electric water pump, or even a torque converter, you've made a poor decision.
Rant over, let the flames begin
08-11-2012, 12:44 AM
#2
Great thread, thanks for taking the time to post this as I'm sure it will be helpful to people researching. I've had a few factory twin turbo cars and know what you mean about the transient response, it feels great for sure.
I have never had a v8 turbo car though, the three I had were all 6s, so don't have a reference for comparison, I can only imagine my smile would be a lot bigger
I have never had a v8 turbo car though, the three I had were all 6s, so don't have a reference for comparison, I can only imagine my smile would be a lot bigger
08-11-2012, 07:33 AM
#4
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I understand your stand on this topic at hand.
My honest and serious issue is people doing a LS swap and throwing as much power as they can at it with stock 8.8 diffs in fords, stock 10 bolts in gm cars, with stock suspension, factory worn out bushings, worn out brakes, etc.
Lets face it, LS engines make some amazing power on absolute junk yard goodness. Now its up to the owner to be responsible to keep everyone safe.
I'm all for something that looks like it should be crushed, making 600rwhp on a stock junkyard swap, ONLY if its actually safe. Good brakes, proper alingment, tires, etc. If it wont pass a local safety inspection, get it off the road.
My honest and serious issue is people doing a LS swap and throwing as much power as they can at it with stock 8.8 diffs in fords, stock 10 bolts in gm cars, with stock suspension, factory worn out bushings, worn out brakes, etc.
Lets face it, LS engines make some amazing power on absolute junk yard goodness. Now its up to the owner to be responsible to keep everyone safe.
I'm all for something that looks like it should be crushed, making 600rwhp on a stock junkyard swap, ONLY if its actually safe. Good brakes, proper alingment, tires, etc. If it wont pass a local safety inspection, get it off the road.
08-11-2012, 09:01 AM
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Jim, I wish you had made this post before I bought my turbo and modified my entire car around it. For us that are not in the turbo ls business day in and out its hard to filter good and bad info. Now that ive gone through a whole bunch of engine,cam,heads, intake,converter,turbo changes I feel I have a very clear idea of how to bulld a matched turbo ls.
On that note, I wish I could afford to fit a larger turbo or twins. Id love to try and fit a bw unit or a, large garret. Just stuck with trying to work with my current space restrictions.
On that note, I wish I could afford to fit a larger turbo or twins. Id love to try and fit a bw unit or a, large garret. Just stuck with trying to work with my current space restrictions.
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08-11-2012, 09:57 AM
#12
I don't know how long I have been PREACHING this SAME thing for!!!
I've been ridiculed when I've suggested "too big of a turbo" in this section for a long time and FINALLY people are seeing this. Where are the people that have told me in each thread I have said this in ALL the time now?!?!? Probably wondering why there turbo isn't doing what they want it to!
The whole package as Intim8 said is TRUE!
You HAVE to match the cam to the turbine you are using!!!
When you have a small turbine you have to use a very small cam with a very late EVO(exhaust valve open). If you put a cam with an early EVO in a 347-364 that has a 68-75mm or even the seemingly popular 83mm and 87mm wheels from borg it's going to put too much exhaust gas into the turbine and make the back pressure situation even worse!
I have also been ridiculed for suggesting cams that "aren't the norm" as far as people that just look at the numbers @.050 and LSA. You HAVE to look at the valve events as a whole and then find an intake and exhaust lobe that gives you the lobe area that a turbo motor needs while not using a radiacal lobe that the valve-train cannot control!
Man preach on brother Intim8!!!!
Added: Then you got the guys that while tuning, wonder why their car won't spool and doesn't come alive until 5500rpm even after choosing the smallest possible turbo they can. Timing and AFR are also KEY to getting a turbo to spool how you want it! I don't know how many people I have helped and fixed their tunes in this section alone that were having trouble spooling their turbo(s) and after I did a few simple things they were blown away by how much faster it spooled.
I've been ridiculed when I've suggested "too big of a turbo" in this section for a long time and FINALLY people are seeing this. Where are the people that have told me in each thread I have said this in ALL the time now?!?!? Probably wondering why there turbo isn't doing what they want it to!
The whole package as Intim8 said is TRUE!
You HAVE to match the cam to the turbine you are using!!!
When you have a small turbine you have to use a very small cam with a very late EVO(exhaust valve open). If you put a cam with an early EVO in a 347-364 that has a 68-75mm or even the seemingly popular 83mm and 87mm wheels from borg it's going to put too much exhaust gas into the turbine and make the back pressure situation even worse!
I have also been ridiculed for suggesting cams that "aren't the norm" as far as people that just look at the numbers @.050 and LSA. You HAVE to look at the valve events as a whole and then find an intake and exhaust lobe that gives you the lobe area that a turbo motor needs while not using a radiacal lobe that the valve-train cannot control!
Man preach on brother Intim8!!!!
Added: Then you got the guys that while tuning, wonder why their car won't spool and doesn't come alive until 5500rpm even after choosing the smallest possible turbo they can. Timing and AFR are also KEY to getting a turbo to spool how you want it! I don't know how many people I have helped and fixed their tunes in this section alone that were having trouble spooling their turbo(s) and after I did a few simple things they were blown away by how much faster it spooled.
Last edited by Sales@Tick; 08-11-2012 at 10:35 AM.
08-11-2012, 10:39 AM
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I can attest to what Jim is saying here... He told me this way back when about my small turbine wheel tc78. I threw my junk tc78 turbo away and stepped up to a precision 7675 this year and the gains were enormous! Never again will I toss a turbo on a car just because it was "a good deal". The rest of the setup costs way too much money to sacrifice performance for a few shekels.
08-11-2012, 10:43 AM
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Great post, I like alot of guys here have never built a turbo car before making the plunge. I have a forged 346 with tu1 cam and tc78 on e85. Spool is so damn fast and although I choke a little up top with the 68mm turbine wheel I have a great power band. People have said I'm better off with a pt88 but I think my sweat spot is going to be a pt7675 to keep spool where I want it. Is this the ideal setup, probably not, but if I had the opportunity to trade my initial setup with anyone elses initial setup I wouldnt.
08-11-2012, 01:13 PM
#17
TECH Apprentice
I understand your stand on this topic at hand.
My honest and serious issue is people doing a LS swap and throwing as much power as they can at it with stock 8.8 diffs in fords, stock 10 bolts in gm cars, with stock suspension, factory worn out bushings, worn out brakes, etc.
Lets face it, LS engines make some amazing power on absolute junk yard goodness. Now its up to the owner to be responsible to keep everyone safe.
I'm all for something that looks like it should be crushed, making 600rwhp on a stock junkyard swap, ONLY if its actually safe. Good brakes, proper alingment, tires, etc. If it wont pass a local safety inspection, get it off the road.
My honest and serious issue is people doing a LS swap and throwing as much power as they can at it with stock 8.8 diffs in fords, stock 10 bolts in gm cars, with stock suspension, factory worn out bushings, worn out brakes, etc.
Lets face it, LS engines make some amazing power on absolute junk yard goodness. Now its up to the owner to be responsible to keep everyone safe.
I'm all for something that looks like it should be crushed, making 600rwhp on a stock junkyard swap, ONLY if its actually safe. Good brakes, proper alingment, tires, etc. If it wont pass a local safety inspection, get it off the road.
08-11-2012, 03:40 PM
#20
Great post like always Jim, I always read your words when you have something to post. I've found a lot of good info in the past just from searching your old post's over on theturboforums. I appreciate all the info you've posted over the years.
One thing I'd like to add is people need to compare apples to apples. A turbine wheel has an inducer and exducer. Some companies rate the turbine size by the inducer and others rate it by the inducer. TC76 68mm exducer 75mm inducer, PT7675 75mm exducer 83mm inducer, BWS400 series with 83mm turbine is 75ish mm inducer and 83mm exducer.
One thing I'd like to add is people need to compare apples to apples. A turbine wheel has an inducer and exducer. Some companies rate the turbine size by the inducer and others rate it by the inducer. TC76 68mm exducer 75mm inducer, PT7675 75mm exducer 83mm inducer, BWS400 series with 83mm turbine is 75ish mm inducer and 83mm exducer.