ddnspider

iTrader: (26)

Id like to know what RPM those runs were made to to get those backpressures.I keep going back and forth in my head about going to a bigger turbo than the T76GTS for my 383 or not.I rarely go to the track and would only rev to prolli 6500 but would backpressure get that bad that an upgrade would be practically mandatory when running 15psi.I like the idea of a low boost threshold but not at the expense of damaging parts.

Pro Stock John

iTrader: (34)

You might want to look at some of the info on JZ's site, but you might want to look into a 80-82mm turbo because it sounds like a 76mm might be done at like 6000rpms... Best do some reading!

ddnspider

iTrader: (26)

Thats the thing,i been reading alot lately.As a matter a fact i talked to Jose about my setup and he told me for my 383:
mostly Track:T88
mostly Street:T76GTS
but with the findings lately i guess im just second guessing myself.im happy if the car makes 600rwhp and doesnt have an issues because the turbos too small.Id like to get him on here to explain more.What turbo did u go with PSJ?

Pro Stock John

iTrader: (34)

600rwhp should be very easy with any of those turbos. The question I think is whether you are hitting a lot of backpressure between 6000-6500 rpms.

I picked a combo that I hope can make 1000-1100 rwhp.

RHall8612

Great post. I love info like that. If you could ever compile a chart of info like that it would be greatly appreciated by many of the turbo nerds here.

If you know, what kind of power did the 347W with the 101mm make? What RPM was peak torque reached? Thanks in advance.

-Russell

2001-WS6

I haven't bothered to put the car on the dyno yet, so my 6300 rpm estimate is based on "seat of the the pants meter" with back up from the Power Meter I-D tied into the Blitz SBC I-D boost controller. The 15psi passes seem to be pretty close to the 6,300 range at this point.

These particular testing passes on the freeway were strickly to determine how much MPH was being lost to the converter at the top end on the drag radials.

Rick

Pro Stock John

iTrader: (34)

You shift at 6300 or higher?
---
Now surge comes into play when the turbo is too big? Do big turbos on small import motors surge?

Project GatTagO

iTrader: (7)

Once again, this is not fact, but how I understand things. A friend of mine installed a Master Power T70 on 4G63T 2.0L engine. It had a .68 AR turbine housing. He said the combination of the small AR turbine and large compressor cause a lot of surge. Keep in mind that boost is pressure. Pressure is a measure of resistance to flow. So this combination of parts spooled the turbo relatively quickly and the the compressor was flowing a lot of air. The problem was that the engine was not able to injest the air and cause a rise in pressure in the intake. This is what is called surge. The condition is such that it is forcing the compressor to operate in the upper left hand section of the compressor map. So a solution to the problem was a turbine housing with a larger AR. This cause more lag, but it allowed the engine to reach a point where it was actually able to consume all the air that the compressor was putting out. This is why high HP small displacement turbo engines have power curves that look very peaky.

Andrew

Pro Stock John

iTrader: (34)

Is that graph on JZ's board showing air/ lbs per minute? If so, what is the baseline for a stock engine? A 414ci LS1 is a nice example but it's a bigger engine than most.

ATTI2D

iTrader: (1)

Good info guys.

LIL SS

iTrader: (9)

John,

Here is an expanded excel spreadsheet showing air requirements of a 346ci LS1 based off the spreadsheet Jose has on his web page. 25psi up to 8,500rpm. I know your not planing on spining it that high but it's a good FYI for you. http://73-ls1.com/misc/Airmap.xls

2001-WS6

I'm shiffing at 6500 right now with a 6800 limiter.

I suspect there have been very few surge issues for our motors and the turbo combos that we've seen to-date. It would be a street problem most likely.

In the world of diesel trucks, you'll run into the fun of "Turbo Bark". We're talking big cubes, 32-40PSI+. The motor not only refuses to take that last gulp of air but the air charge actually causes the compressor to shudder stall making a nasty sounding bark. It's not the most pleasant sound when getting off a freeway pass.

Rick

Pro Stock John

iTrader: (34)

Nice spreadsheet Shaun!

So I could theoretically be in the 100 range a lot, how about you guys?

y2khawk

iTrader: (5)

Mine use to surge at idle, and low RPM. Anything high enough to actually get movement out of the converter and the engine way using enough air to keep them happy.

y2khawk

iTrader: (5)

Can you run that out to 37 psi and 9k RPM? Or send me the math you used? I'm curious to see how my math matches up

And yes i'm serious about 37 and 9000

LIL SS

iTrader: (9)

Depending on boost level, these are my requirements lb/hr

1st gear shifting at 8k / 10psi I only need 77lbs
begining of Second (5,400rpm) 10psi I need 52lbs - 77lbs at 8k
begining of Third (6k rpm) 10psi I need 58lbs - 77lbs at 8k
begining of Fourth(6,200rpm) 10psi I need 60lbs - 77lbs at 8k

So at 10psi I will never need more than 77lbs at 8k.




1st gear shifting at 8k / 25psi I only need 126lbs
begining of Second (5,400rpm) 25psi I need 85lbs - 126lbs at 8k
begining of Third (6k rpm) 25psi I need 94lbs - 126lbs at 8k
begining of Fourth(6,200rpm) 25psi I need 95lbs - 126lbs at 8k

So at 25psi I will never need more than 126lbs at 8k.


This is based off the stock airflow of an LS1. I would assume that these numbers would be higher with a better set of heads, intake and exhaust as the air flows much easier.

The PT91 I plan on using should support in the 135lb/hr range.

LIL SS

iTrader: (9)

10k to 45psi

http://73-ls1.com/misc/10k_45psi.xls

JZ 97 SS 1500

iTrader: (2)

Yes VE will go up indeed with a better flowing engine. I have those maps as well, but I don't post them.

y2khawk

iTrader: (5)

Any density ratio correction, or just straight volume/PR/mass conversion?

My math is close

JZ 97 SS 1500

iTrader: (2)

Yes we can alter it with after intercooler temps. Let me know what you expect in form of IAT's.