Anyone rocking or try out the new VS racing billet 70/70 .96AR turbo? Viren says new tech, billet wheel small frame turbo good for 1100hp on smaller applications on a 5.3 that would be good for 650-700 hp with fast spool. Think between 76/65 and 78/75 with and the S366 66/73 turbo. I'm not too thrilled with the price but boost should be quick and spin to 6500.

 

IMO if you're talking 5.3, I'd be targeting 7,500rpm at minimum for peak power, anything below that and you're leaving power on the table.

 

Never gona spin that high! This is a street car so I'm looking for boost to start sooner and peak by 6000-6500. My cam is only designed to spin to 6500, motor has gen 3 rods and makes plenty of power with a VS Gen 1 billet 78/75. My issue is with a 2400 stall I'm only starting to build boost around 3k and thats fine as shes a rocket once it comes online but I want that to come on like 2500 so I can enjoy the boost easier on the street. My 72lb injectors will only support 750hp on 93 which is alittle above 16psi. This is not a max peak power, I want more power under the curve and something that will rev to 6-6500k and then be all done. Most of my driving is idle to 4500 around town and I get to blip it on the highway etc.

 

This may be a stupid question, but it can't hurt to ask......have you tried playing with timing and fueling down low? I've noticed that timing changes and leaner mixture right before it comes online, leads to quicker spool. When I put my 1.25 housing on, i was able to tweak it and get the spool to about what it was when I had the .96 a/r housing. Just an idea.....

 

yea I posted my timing and fuel tables in another thread and I was told it was decent. I basically run NA timing and fuel till a few psi and then Ramp it down. See my timing and fuel below.

 

I would be very careful with that timing hump at 2500RPM...

Andrew

 

^that. also 29.4* seems excessive at 3000 on. Also why 13.5 at WOT NA?

and if the filename is any indication having a cat on a turbo car just sucks for spool.

 

What do you suggest? Are you talking about the 2000-2500 133kpa blip?

 

I would first step back and rethink the scaling for the whole table. There are 33 rows in that table and 2/3 of them are devoted to boost, which is completely unnecessary. Cathedral port heads don't like a lot of timing at low RPM and high load NA, and that even more so in boost. I am not going to give you specific numbers, but I can tell you what you have is way too much.

Andrew

 

I thought LS motors wanted around 28* around WOT... I could lower than to 28 and redo the timing table. My cam only pulls 14" at idle so cruising I was trying to keep the A/F around 14.7-15:1 for the MPG. I can richen that up but It really only gives me 2 rows to drop from 14.7 to 12.5 and I was trying to keep it on the leaner side until 133kpa+. I'm not a professional tuner so I'm always open to suggestions.

Your CAT assumption is correct, its a 3" high flow metallic 200 cell CAT that I put into my transition from the 3" DP to my 4" Catback right after the cutout. I don't see much from the cutout being open or closed with the CAT installed and it has cut down on the smell a good bit after its been warmed up. I drive this car to work in the spring/summer and I can't be smelling like crap in my good clothes lol. Opening up the cutdown does add some power but not much and I get more turbo noise.

 

Great! lol. So I'll yank a few degrees out and try to smooth it all out. This table is light years ahead of the Fitech table which was like 10 lines for vacuum through 3bar.

 

I would seriously give some thought as to how you want to scale the load axis. Ten rows for boost is more than enough, even for 20 PSI. I would devote 2/3 of the table to NA and 1/3 to boost. Also, just because you are using the 2.5 bar MAP sensor, it doesn't mean you have to scale the load axis to the limit of the sensor. Pick whatever max boost value you are going to run and add a couple of PSI and that should be your top row. As a result, you will obviously have to completely reshape your VE and your spark tables, but you will be rewarded with a lot better drivability. Other things of note, you don't need to start the load axis at 0kPa, a floor of 20kPa works well. You also have too much timing at idle if you are using a turbo friendly cam.

Andrew

 

This was just how the table was scaled in Holley... I can see about editing that. However my timing and the drive ability isn't an issue and the car drives great. I'm just trying to get boost in a bit sooner for more fun in my operating RPM range on the street. I can see the A/F table being broken down to help with fueling at closer MAP points for more control over the fueling and we will about that as well. My cam is a custom blower cam from Cam motion 218/228 .561/.561 115.5+4.5 and they said it should make 18" at idle of like 600 and I have never been able to get it above 14" even at 750rpm.

 

I've never had a small cam LS want 28*+ on pump gas, especially when its choked up by a small hotside. You can't just throw numbers in there you need to see what it actually wants. Have you read the plugs? I would start a lot lower, I dont even run 28* on E85. You dont want it to be so lean its costing you power, no need to be over 13:1 at all. You can rescale those rows any way you want to get resolution where you need it.

 

I wouldnt call a 78/75 .96 AR on a 5.3 small or choking. I also have limited space and need a small frame turbo for everything to bolt up. It's hard to know what it wants without a dyno. I have had the plugs out and they didn't look bad, no detonation either. It could be the water/meth thats preventing any at the moment since the timing seems high according to people on here. I can easily knock out a few degrees but I have never fussed with it as it has always run fine. I have played with the timing but can't say I have really tested the timing to figure out what it wants. I was more getting the fueling and timing in with the new holley and making sure it was working as it should. Prob had the car out 5 times or so before storing it for winter with the holley. The Fitech was on for a few years but the resolution on the timing table is crap but timing was probably similar and ran fine. What is typical timing for a small cam 5.3 on pump? Your saying to tune it at 13:1 at idle and cruising? I'm not looking at squeezing max power on cruise , in the lower map ranges I want it lean for the MPG and Its very easy for me to be at 76kpa on light throttle. Hence the 14:7 as I can cruise there with the converter locked as I load the engine pretty easily. I will look into re-scaling the tables though as that's a good idea and I can work on that over the winter. I really need to sit down and look at the holley system and how to use it including how to log correctly.

 

You also stated in the other thread that you want boost 500-1000 rpm's sooner. Adding a half point of fuel and pulling a few degrees isn't going to fix that.

 

Correct, VS racing says the 70/70 will spool 500rpms sooner than my 78/75 and support the 650whp range and be all done by 6500... sounds perfect. Maybe I can mess with the tune to see if I can make that even faster. I will let you guys know in the spring how it does . I know I won't get the spool without a smaller wheel turbo and realize It will limit HP potential and RPM but you need to pick the turbo based on the usage and power levels. I dont need more than 650whp and I dont need to spin above 6500 so 70/70 it is. I will mess with the tune as well as I want this to be safe and last a long time. I originally got the 76/65 from CX with the turbo kit and then I was told the 7875 would spool the same and offer more power in the mid and upper ranges due to the larger wheel/exhaust housing and the wheels are closer in size for a more balanced turbo (or it should be bigger on the exhaust side). From some reading I've been doing says that the 78/75 tend to spool 3k+ on a 5.3 and the sweet spot for a lower rpm 5.3 is 60-72mm and and equal or larger exhaust wheel and the .81-.96 AR. I felt like the 76/65 choked on the top end like it nosed over due to the exhaust wheel with the .81AR housing and I think a 70/70 .96AR would be the sweet spot providing faster spool than the 76/65 + 78/75 and come in harder/sooner for street driving and still let me rev out comfortably to 6000-6500 for the 5% that I actually get to. Seems the 76/65 will max out the 65 turbine before the 76 is optimized. The 78/75 is a more balanced turbo but still slightly too large on the compressor size for the small frame. I would have like to see a 67 or 70mm compressor and a 75 ish exhaust wheel for my combo (can you say S366) but the size of the turbo will not fit on my application and would require way to much modification to fit and I would be limited by the 3" Vband down pipe.

 

A 75mm turbine on a V8 is small, you will have backpressure, backpressure requires lower timing. Thats why often you see guys going to an 88mm turbine and it spools faster as it lets the engine breath!

I said your 13.5:1 at WOT NA was lean, you can idle and cruise at 14.5-14.7:1 just fine, but the engine needs fuel to make power when you push the loud pedal, so giving it some fuel 12.7:1 would be good starting point there, I wouldn't go leaner than 13:1 in that range which is what I was saying.

 

gotcha, I’m gona see how to rescale the tune and see if I can get more data points in the MAP scale and will riches it up below 13:1 at WOT. Realistically I’m through the 95kpa range at half throttle rolling into it. I will also look at taking a few degrees out in the whole tune and adjust the scaling in the timing table maybe to 200kpa.

 

The Y axis is load, and with a speed density system like the Holley, it is approximated by using manifold pressure/vacuum. This is measures in units of kilo pascals. (kPa). In a normally aspirated engine, anything below (generally it is hard for an engine to pull down below 20kPa, so many MAP sensors are actually 20kPa to 105kPa for a 1 bar sensor) 104kPa is vacuum. When the manifold pressure equals that of barometric pressure, the engine is under as much atmospheric pressure it can be on that given day at that given location. Anything about 105kPa is boost, or pressure above atmosphere.

Keep in mind throttle position has an impact on manifold pressure, but they are not 100% correlated. You can have a relatively small engine, with big throttle bodies, and achieve full MAP at 50%TPS. You can also have an engine with a large turbo, and you might see TPS go to 100%, but the MAP will continue to rise as boost pressure increases. This would also be the typical situation if you had a centrifugal supercharger, where the output (speed) of the compressor is directly correlated to engine RPM. This is obviously not the case with a turbo.

Andrew