fast82z

iTrader: (1)

I've been involved with this thread on yellow bullet about compound turbos: http://www.yellowbullet.com/forum/sh...d.php?t=216811 and learned some fantastic stuff, specially by the time of my last couple posts. I have come up with methods and calculations to tell me just about anything about the turbo/blower aspect of a forced induction setup, or at least the intake side since I have yet to understand the exhaust side 100% in calculation form. The root tool that enables me to do this quick and accurate is a free program called cyclepad that you can google and download. Basically in any problem I start by finding the volumetric flow of a given engine, and this can be found in many ways and is a constant for that engine. Then I can vary intake pressures, temperatures, or flows and just read off any other numbers that change to tell me about anything in the setup.

For fun, and to help test these methods, I welcome anyone that can give me quality info on their specific application. Some things I can do: Turn n/a hp (or 1/4-mile mph and weight) into a hp (or 1/4-mile mph and e.t.) at any boost pressure, and tell the air flow (turbo or blower size) needed to accomplish this. I could do that backwards and tell the n/a hp/e.t./mph. Find the hp/e.t./mph gain by adding more boost. I could find the hp gain by dropping intake temps (intercooler). I can find out how much boost a given turbo could make on a given engine, and the power made at this pressure.

Should you want to mess with this yourself, I can email my model in the cyclepad program that I'm using although proper information from this requires knowledge a little beyond what I've said here.

Orr89RocZ

iTrader: (20)

Never seen this thread til now...

Let me run this by you... my setup with twin 60mm turbos, vs twin 70mm turbos...same turbine Ptrim, both same brand turbos just larger compressor. Wondering if I will see much of a difference (I think I will) as I think the 60's are small for a 401 and the 70's should be more efficient thus giving less heat to the compressed air. We shall see

I have my own spreadsheet to estimate power, trap speeds/ 1/4 miles etc and it does well with the right inputs, but curious to see where you put me.

401sbc 9 to 1 compression with afr 195's (280's cfm), 233/233 hydraulic roller, .564" 112lsa 110ICL, peak power around 5500-5700 rpm my guess, single plane efi intake.
60.5mm/84mm ind/exd compressor with Ptrim turbine wheel, was .68 a/r and may remain there. Has gone 9.86 at 141 on 14psi on a good air day. 650-ish whp mustang dyno at that boost. No idea what IATs were but hoping 70's will pass more air and get this car turning. I'd like to get near 150mph

fast82z

iTrader: (1)

This is what I ran through for that: 3600lbs at 141mph = 785rwhp or 980fwhp. Your pressure ratio is (14+14.5)/14.5=1.966. 980hp/1.966 = 498hp n/a engine. To get 150mph out of 3600lbs it takes 950rwhp or 1190fwhp which should take you 1190/498=2.48 pressure ratio or 21.5psi. To place this on a compressor map, the max point would be at about 2.5 pressure ratio and 60lb/min. These numbers put you at the edge or just off the compressor map of 60mm's with total max turbine flow of 66lb/min max. On 70mm's map, you'd be right in the meat of it in the max efficency area with total max turbine flow of 76-90lb/min depending on the a/r. I've been looking at what changes exhaust backpressure and more turbine flow is a primary way to reduce this, which increases power.

So, by going with the 70mm's you get a two fold effect by having more efficient compressors capable of more power, and less power is lost since the 10+lb/min gain from the turbines will make for less backpressure.

Orr89RocZ

iTrader: (20)

Seems along the same lines as my thoughts. I predict the 70's to be in the meat of efficiency while the 60's I was walking up the choke line.

Now I just need to decide if I want to go with .68 a/r housings on the turbine or .96's. I have both laying around. Turbos have same Ptrim wheel, and I liked how the .68's were ridiculously quick spooling, but I am curious if that is hurting the top end by becoming a restriction. .96's with delayed spool will help keep traction while reducing backpressure I'm sure, giving more top end speed/power. I'm leaning towards the .96's since most guys running 3-3.3L motors would use .96 for 400-500whp...basically half my motor

fast82z

iTrader: (1)

Don't remember what post it was, but I know a guy on the bullet hooked a check valve and pressure gauge into the exhaust before the turbine to see back pressure. My ecm has a connector for a pressure sensor for me to log exhaust pressure that I plan to use next season. I've been at least glancing at others 4 cylinder stuff too since what we're looking at is basically double that. I've gone with these cheapy ebay turbos that have T4 1.05 a/r housings that should flow around a total of 70lb/min vs. my 91mm turbine that flows 58 with the 1.0 a/r or 70 with the 1.5 a/r. If the twins do end up too laggy, I should be able to pipe the turbines in series to bring up spool much faster while switching back to parallel for peak flow.

Orr89RocZ

iTrader: (20)

Since my setup is apart, i may weld in a bung for back pressure measurements... Always curious to see what mine are doing.

Eric89sc

iTrader: (1)

Hey guys I'm interested in seeing how you figure all of this out. I have been fighting with my car for a while and it would be nice to calculate what it should have before I go to the dyno again this spring with a new convertor.

fast82z

iTrader: (1)

Usually what I do is start with what the motor can do alone, either by the combination of parts and estimation, or more accurately by vehicle weight and 1/4-mile mph. Take that n/a fwhp figure and multiply it by (boost pressure + 14.5)/14.5 to get a good estimate of the boosted fwhp. Or if you have a target fwhp, this will give you a good estimate on the psi needed to make that power with the engine being used. I wouldn't expect these numbers to show up on a dyno though. From what I've seen, cars that show 700's rwhp by their 1/4-mile tend to read in the 600's on a dyno.

camaro_V6_Tuner

Wow, this sounds great! Well here's one for you.

327 engine with 8.4:1 cr (or 9.55). 3500lb car. Trying to figure out which turbo to go with for 11's @ around 125mph in the 1/4 with the fastest spool possible.

Also throwing around the idea of a 350 with 9:1 cr, same times & speed

fast82z

iTrader: (1)

Seeing as how 11's are quite possible without boost, this wouldn't take much turbo at all. 3500lbs at 125mph shows 670fwhp, and should actually run a 10.90. Minimum sized single should be around mid 60's mm and twins around 50mm. Think I'd go with one of the one's that I'm using for twins that's almost 70mm since it's cheap and a few people seem to have good luck with them. Like this one: http://cgi.ebay.com/ebaymotors/GT45-...Q5fAccessories From some numbers I've ran and have seen, this one should be good for 800hp maybe 900hp if you really push it.

camaro_V6_Tuner

I guess that just means my car can be faster than I had hoped! Sounds good. i can't wait to start this project.

Eric89sc

iTrader: (1)

Orr89Rocz I saw that you said your car dynoed with 640 rwhp on 14 lbs right? If you do the equation what does it say your fwhp should be? Just wondering bc when I did it the numbers come out really high for my car.

fast82z

iTrader: (1)

At 14psi, you're looking at almost double the hp from what it'd make n/a since absolute pressure has gone from 14.5psi to 28.5psi, so on motor only probably about 320rwhp.

Orr89RocZ

iTrader: (20)

640whp on 12.5 psi on a mustang dyno thru a very loose converter in a Th400 trans. Theres alot of loss thru that driveline and mustang dynos read lower than dynojets and some others. My best trap on 12psi was 139mph so far. 14-15 psi seems to get me 140-141 depending on air quality. I like to think my motor is in the 800-850hp range at the crank on 14-15 psi

401 cubes with AFR 195 heads and 233 deg hydraulic roller is great recipe for 340whp on dynojet my guess at 9 to 1 compression if I was to run this on motor. If you do the 14-15psi = double n/a hp, that puts me in the 680 range. On the dyno, thats pretty close.
Even on motor tho, this 401 is pretty stout. Its got a cam thats about as big on the intake lobe as my 383 was with the same heads, and similar intake. My 383 was 400whp... this 401 i'd be happy with 340whp...I dont think thats asking for much.