Is there a how to on here or on the the net about how to read a compressor maps?

I know there is a correct air flow axis and a pressure ratio axis but where would a 2.0 engine be within these axis? lest say a 2.0 Audi A4 20v, Cossie engine and 1600 cvh?

 

http://www.vauxhall-sport-forum.com/...urbos-t92.html

 

That's a great explanation Chip, I used to look at them and my eye's would glaze over, now I kinda know what to look for if I ever need too!

 

Thanks.

I know that I wrote it and hence im massive biased, but I think its the best explanation ive seen to date in terms of getting across the basics people need to know, its easy to overcomplicate the subject too much, I was aiming it at people who know NOTHING about these maps in the first place and most people in that situation who have read it have said like yourself that it made a big difference.

 

Yea it's definately v.understandable, I have some knowledge already on turbo's but I reckon if I had a very limited knowledge on them i'd still understand what you were trying to tell me. I've searched before to find out how to read one and frankly I got bored as you say with over complicated explanations.

for a GT4294R I've came up with:




Max BHP - 850
Max Boost 3bar
Most efficient - ~540@1.5bar

 

Yes mate, thats all the correct ballparks

But one thing to note of course is that although it will do 3 bar of boost, it will only do it at around 500-600 bhp not at full power.

So would be great for a massive amount of midrange torque (like madrod had with 666lbft on pretty much that turbo IIRC) but not great for trying to hold the boost right up to the top of the rev range, at the top end it only wants to be doing 2-2.5 bar

 

Ah yes I see that now! My mate's going to be using that exact turbo on his RB30 (3.0 version of an RB26) for ~7-800bhp. should be interesting!


cheers

 

I just read that bit in my book yesterday and your simplified way is much easier than trying to get the pin point using the calculation of...

(0.5 x CID x Max RPM / 1,728) x VE x DR x 0.069

Mind you it is good to understand where some of the numbers come from and how you achieved them.

 

good explanation that chip cheers

 

great explanation, i've always wondered how they work- so simple when you know how huh

 

fuck me i can read a compressor map !!



chip you should start helping stu with his ff articicles lol


but nahh really useful mate !!


much appriceated


beef

 

Good read chip, is what you say about chatter (surge) being harmful to the GT (BB) range of turbo's accurate, I hadnt realised this?

 

Yes, their shafts are thin so they suffer from movement if they are chattering too much.

I believe it was Martin hadland on here for example that had some problems with his original GT35R engine and ended up needing a larger or twin dumpvalves in the end to cure it (think it was him anyway)
Its only when running big boost though, chatter away all day at half a bar and you're unlikely to have a problem.

 

Cheers Chip, good to know if I ever end up running a GT turbo

 

Empowering isnt it? When it stops seeming like black magic!



I do the same sort of articles for Total Vauxhall that stu does for Fast Ford anyway mate.

Out target audiences we pitch at tend to be slightly different though, generally mine are a little easier to read, but his contain more detail, which is just down to the perceived average knowledge of the reader I guess (and possibly down also to Stu's greater technical knowledge than myself of course! )
I think the typical fast ford reader has been in the ford scene and reading ford mags for longer than the average total vauxhall reader has though for example, so its a safer bet to assume they know a bit more of the basics already.

 

I know you've got a great job already but youve honestly explained that so well that I think you should consider a career in motorsport lecturing at some point as that's really clear and understandable.

I can just see you in a sports jacket smoking a pipe on campus with some brown slacks and full bumble beard!!!!

Seriously though,really well written.

 

Great article chipper!

I have actually written one too.
http://www.motorsport-developments.c...AF241.tech.pdf

(Edit: Read yours properly now and its more user friendly and idiot proof than mine, nice work.)

 

Thanks, means a lot coming from you.



Predates that forum reply I wrote by about 6 months, and I normally make a point of reading all your articles when my fast ford subscription comes through each month as I always enjoy them, so I was probably inadvertedly influenced by yours anyway then even if I didnt know it
Impossible to read a good article, then write your own on the same subject and NOT copy some of it unintentionally!


As I mentioned earlier, we have slightly different target audiences generally, so yours are invariably more technically detailed, it would be impossible within the limited word counts we work with to manage to score 10/10 on both the accessibility to people who know nothing on that subject front and the giving enough detail to be useful to people who are already fairly familiar.

If people read mine first, then yours after, I think they'll be able to REALLY understand compressor maps in the space of only a couple of hours, which is good cause it took me fucking months to get my head around them with no decent reference

 

chip great read.
is there away of putting a gtx3071 compressor map over a gt3076 to show the difference?

 

They are published on different axis so you'd need to manually do it.

I saw one that someone had attempted for a gt3071 and a gtx3071, but TBH it wasnt great as I checked some points for each and all the 3071 ones I checked were slightly wrong, so it looked less favourable than it actually is.



That is it, but I disagree with it, hang on will grab the GT3071 map in a sec and show why!

 

Here you go:



The whole surge line on the "comparison" one, is too far to the left IMHO for the GT3071, so makes the GTX3071 look like its worse in this region unfairly.

Look at the 30lbs point for example on the map in this post, and the one in the comparison, in the comparison it shows the gt3071 as over 3 on the pressure ratio scale, but on the actual map its actually only 2.8 or so, and the GTX3071 is actually 3:



So that comparison makes the GTX look worse, when its actually better at that point!

Not sure why they made that mistake, or if I have somehow misunderstood what they are trying to show!

 

cheers.

i just cant make my mind up which turbo to go for.
the gt3076 is cheaper
and know one has tried the gtx3071 to see if it spools up as quick as the gt3071 and will spool quicker than the gt3076

 

Have done just that and have a great understanding of comp maps again now!
I do remember reading Stu's in FF but had since forgotten it all having no need to use it regularly, great refresh

Is this an error in Stu's article?



Shouldn't it read 10bhp = 1lb of airflow, or have i missed something?

 

Yes mate you are correct, it should ready 1lb = 10bhp not the other way around, as it is on the line above and as it is in my one.

Stu's comment of 9.5 - 10.5 is actually far better as it shows that not all engines have the same bhp specific air consumption, which is actually quite an important thing to understand, two turbos the same on different spec engines wont give the same results even for the same amount of air flowed.



Also the same goes for if you change your AFR, although we're then off into a tuning article really, lol.

But basically at 12.6:1 AFR you might see for example 10 bhp per lb at a particuarly point on the map, but at 11:1 on the same engine you'll perhaps see 9.8 instead

 

Cheers Chip thought I'd just check!
Nice informative techincal thread this and no arguing! Nice

 

Damn it, I proof read every one of my articles three times and I still manage to miss something like that! Gutted.

 

Me too, which makes it infuriating when you buy one, bolt it on and its still shit after all your hard come by research. LOL

 

lol
I proof read my posts at least three times and still have to edit them afterwards because of spelling/grammar, 'wood for the tree's' and all that mate.

 

Its a bitch not having an "edit" button after 10,000 copies have been printed

I made a similar fuckup on an article I did for total vauxhall, really wound me up when I noticed it after print, I really am VERY thorough with checking stuff but sometimes your mind just reads what you meant rather than what you wrote, so its not till you see it 2 months later in print that you read it fresh for the first time and realise!

 

I proof read mine none until after ive hit submit, then quickly glance over them on the screen, thats why I so commonly have "edited by" on my posts, I find it easier to read once submitted than in the edit box.

 

LMAO

The problem is, you are making that mistake despite having a very good understanding of the turbine map too, what chance do the general public have, as even if they DO understand compressor maps, they often dont understand the turbine map.
But even knowing both, its still just a fucking guess really

Trial and error is the ONLY way IMHO!
Which is what makes using a tuner reasonable value, yes you'll pay more than DIY, but its a lot cheaper buying one turbo with a markup than 3 without

 

Sooo true. LOL

 

Great little read there, cheers Chip