So he should be looking at larger turbos that have their flow map over that line you've drawn?
Yes and no , that line is purely based on the simple maths to calculate the values , for instance the VE is set at 92% at 7250 rpm and 98% at 5000 rpm - these are not real world values and ours maybe a lot less
take the gto which some figures were generated for full load as 91% at 2000 rpm, 95% at 3000 rpm, 93% at 4000 rpm, 90% at 5000 rpm, 81% at 6000 rpm, and 75% at 7000 rpm (from 3si)
now if we use those as the basis of the calcs we still need 302 cfm(23.1 llbs/min) to produce 225 bhp at 2 bar with a typical afr of 11.2 , this gives us a Pressure ratio of 2.94 which pushes even further away
Think the main point I'm trying to get accross is that there is a lot more to consider about the turbo selection than just selecting one cos it "should" work but looking at the td04-13g which Gowf had they seem to be a very good match to the VR4 engine
If we could work out the VE for the engine then we could plot some real world figures , for instance if the vr4 was 90% VE @ 7250 we would only need 1.5 bar to get 225 bhp froma PR of 2.4 , but at 75% VE we would need 2 bar for 225 bhp from a PR of 2.94 - this has a huge impact on the turbo selection .
This is something I've been meaning to get my head around, but obviously haven't. I'm guessing working out the VE of the engine would require measuring gas flow rates into and out of the engine?
what we need to do is measure the VE of the engine at various points in the rev range ( 2000,3000, 4000 etc etc ) to do this all we need is to know the relationship between airflow single ( hz ) to CFM ( or we fit a seperate CFM meter in the inlet side ) . With this we can then calculate the exact values which help in working it out , we may have a very well design setup that allows greater than 100% ve (F1 cars can have as much as 117% ve )
for people thinking what the hell is VE , well it is the difference between what the engine can breather on paper versus what it does breath
so a 2.5 litre engine should be able to breath 2.5 litres of air , but becasue of loses due to the design of the inlet , exhaust etc we will get less , but as we are charing the air at nearly double normal pressure ( remember we are always at 1 bar ) this offsets some of the loses
Just thought I'd add that VE means volumetric efficiency. From http://www.installuniversity.com/ins...n_9.012000.htm "Volumetric efficiency is the measurement of how close the actual volumetric flow rate is to the theoretical volumetric flow rate"
hmm very intresting. in stating the VE I have planned to fully flow the heads and with custom exhaust mannys and possibly plenum modifications should this raise the VE?
the guys at turbo care here in chch told me they were making 600hp on a 2jz (yes i know its a 3l not a 2.5) with stock internals and head so with forged pistons running a leaner ratio and head work...
also spec returned this thismorning
Supply forged rods & pistons 6A13.
(depending on exchange rate at time of order).
$2,782.61
PLEASE NOTE ESTIMATION ONLY;
Subtotal 2,782.61
TOTAL GST 15% 417.39
TOTAL NZD 3,200.00
thats including rings also
still waiting for a price on bearings though
Anyything that imporves flow will have a good effect on VE
i beleive its is wiseco pistons with pauter rods, IIRC this is the same set that the russians used
rods and pistons do not effect the calculations , it's down to the displacement of the engine
yip i know rods and pistons wont make a difference but i am posting up as much info on parts as i progress through this build
John, you say this: Manifold absolute pressure = 18.55 * number of turbos (absolute PSI)
Why is that?
If I'm replying to your thread and helping you out, it is because I like you and want to help out your VR-4 ownership. No other reason
Hey john what is your opinion on this turbo
http://www.turbobygarrett.com/turbob...R_700382_3.htm
gt3071R
similar price and same external dimentions but bigger turbine and compressor wheels so more flow the higher rpm dot which you calculated before lies in garretts graph. the only worry for me is i wonder the lag with 2 of theese monsters
Adam what is your total estimated horsepower on the new build , and where do you want the powerband to be ( mid range , high rpm ) what sort of boost are you looking to run
with these figures i can throw them into my calculator and come back with the numbers you need to plot agains the flow maps
gt3071r's will never spool! You'd be making boost above 5000rpm or so, and you'd need to rev all the way to 8500rpm to have a usable power band. Stick with GT2860R's
im looking for around the 500 mark if possible. depending if the crank can handle it push the redline up a tad and a fair whack of boost (or what would be the point forging it)
you think brad?? its the same turbo as a gt2860rs just with a slighly bigger compressor wheel by my understanding (same compressor housing, core and turbine housing) when do you think the 2860's will come onto boost in theory, i read the thread on oz vr4 where the guy put 2x gt2560r's on his legnum and he said lag was barely more then factory, instead of being on full boost by 2250 it was 29-3000. which isnt to bad
Adam ok will work out the figures to allow you to hit around 500 bhp with good mid range
that would be much appreciated. i still want to make power but still street drivable. the engine thats in the car at the moment will be going into something else that will be the lag monster engine
My goal is 300kw ATW which is around 500HP or so at the engine, so similar to Adam. I want these ones http://www.turbobygarrett.com/turbob...R_707160_7.htm
as aparently the gt2860rs has better flow then the 60r any particular reason for choosing the 60r over the 60rs
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