Whoa awesome reply thanks John
D - I'm going to investigate water injection once I have it running ok and im in the tweak phase.

John I also agree with your logic with regarding getting spooling happening by 3k and near full boost by 3.5k

So you think the nissan exa or pulsars turbo would achieve that?
And if I wing it with the s13 t25 sounds like that will be more like 4-4.5k?

How hard is it to adjust/change inlet and exhaust manifolds if I get it made for the s13 T25 and wanna swap turbos down the track? Plasma cut & weld new flange?

Bruce Lees favorite drink?..... WHAAATAARH!
The owner of the crude turbo A15 in a vb10 1000 wagon runs a very crude windscreen water unit setup into his draw through as it gets atomised perfectly in the turbine.
His Log style manifold setup gets up to 30psi but cant find his username atm.

Whilst your friend's math isn't 'wrong' by any means, it does however come across as if he thinks it has to be a big dollar perfect match or it just won't work.

In real life, especially 'the ghetto' - you will find you can actually get away with a lot. fwiw I think you should be looking for another turbo - and if possible one off a nissan exa or et pulsar (same engine/spec afaik). I had one of them on a 3k corolla motor and got it into the high 14s (with absolutely EVERYTHING done wrong - smaller motor, crappy flowing pollution era head (you have a bigger motor, and a much better flowing head) and a j pipe that was nothing short of an abortion (the funnelling down from the twin outlet cast iron exhaust manifold was atrocious,the j pipe itself was 2 1/4 inch diameter - too big (slightly smaller keeps the velocity up) and the flange welded on the other end to mount the turbo to - since it had to sit over a 2 1/4" pipe (whereas a 1 3/4 or maybe 2 inch j pipe absolute max will be easy to gently funnel into the flange without an obstruction) - well it was like a big parachute, horrifically inefficient).

despite all that, it ran hard. If you ran a similar turbo on your a14 it would surely be able to run a low 14 without spending stuff all.

I'd like to make a point 'against' laggy turbos. Obviously it is all relative, so there's 'a little bit' of lag that might not be a problem, then ther is a ridiculous amount. as an example - in the US there were 2.3 litre 4 cyl turbo fords (mustangs) from about the mid 1980s. They were discussed a lot on the jyturbo list. Anyhoo, they mostly ran almost identical turbos, but some had 0.48 a/r exhaust housings and some had 0.63 a/r . the larger 0.63 ones produced more power, due to less exhaust restriction overall. However, despite that, on the street, the vehicles with the tighter turbo would always get a few lengths ahead (and maintain it) taking off from a standstill. The reason is simple enough - they spool quicker and get into 'big power' (relatively) sooner and start accelerating hard sooner. The others spool slower so even though they eventuall make more power, they spend more time 'getting into the swing of it' and get left behind so to speak. On the street, better spool (well not so tight on the exhaust that you can spin the motor up to 4500rpm or something!) will be king. It's not just good off the mark, but things like overtaking - the quicker you can access boost/big power the better the outcome. Another place you can see it is some of the 'flagships' of certain turbo workshops. They have a car - once upon a time the VL commodore was the big one here - that they have one of their top of the line engine/turbo combos in. And there's footage of it at the dragstrip and the car runs some absolutely exceptionally quick et/high mph. Which is admirable. But if you look at it closely, they are just running to get a good time (and remembering the 1/4mile et timer only starts once the car actually starts moving and breaks/passes the beam under the front wheels, so they can sit there forever and not be 'running up the meter') - and they'll often spend 5 seconds or so spooling the turbo up so they can launch optimally and run hard. that's all well and good, and whilst it produces a quick time, in a 'real' drag race, a car that spools better can launch harder (and in drag racing the winner is the first one to the finish) will launch, and beat the 'quicker' car to the other end. The 'quicker' car - the driver either needs to launch earlier (than optimal, but I don't mean red-lighting by leaving too early) and without full spoolup, and therefore run slower, just to get off the line in time. He could wait and spool it up so it launches harder, but all the while the 'slower' car is charging further and further away.

So how much lag (or lack of it) is acceptable or not. Well - it differs from engine to engine and car to car. Since we are dealing with smaller engines (that can handle ok rpm without much work) 'ok' spoolup rpms can actually be a little higher in the rpm range than a turbo you might put on a much bigger engien that revs lower overall. So that in mind, I'd suggest that if you can get it starting to spool just prior to 3000rpm, and getting to useful boost (or nearer full boost) by about 3500 you'll be pretty happy with the result.

I absolutely agree that e85 (or e-flex which I think varies down to around 75% at times, but don't quote me on that!) would be perfect for this. But if 98 it has to be, then it's still going to get a good result. Water injection is your friend, and works exceptionally well. You can read about early work on water injection if you look up 'naca reports' (NACA was the forerunner of NASA, and was a tech/research sort of thing for all things aircraft development related). They tested various engines (often to destruction) with higher and higher boost levels and ever increasing water levels. water injection was used on ww2 fighter aircraft (when combined with higher than normal boost levels, for short during emergency high power for stuff like dog-fights) fairly extensively. They (NACA) went as far as actually exceeding a 1:1 ratio of water to fuel (i.e. for every litre of fuel being fed into the engine at full boost/power, they actually were feeding in MORE than 1 litre of water) - and it was still effective up at those levels. On most automotive applications, you'd rarely find anyone going beyond maybe 4:1 (for every 4 iltres of fuel used, and yuo can calculate that based on power output - anyhoo for every 4 litres of fuel, 1 litre of water is added).

They say you need a richer mixture under boost to help prevent detonation. This is certainly true. what not everyone knows is 'why'. It's not because the fuel burns dramatically differently. Run richer and there's going to be some unburned fuel going out the exhaust. It's actually the cooling effect of the extra fuel that cools the intake charge a little bit that helps prevent detonation. This is where it gets interesting. Since it is the cooling effect, and testing has backed it up 100%, well if you added water injection, then that water could take the place of the extra fuel, and it would take care of the cooling effect. I'm not suggesting you should lean it out way too far and then run water and hope for the best. What i am saying is that instead of (hypothetically) going as rich as perhaps 11:1 as you run more and more boost, you could run around 12:1 a/f ratio and add as much water as is needed to handle whatever boost level you are going for.

That graph your mate plotted doesnt have an 80 trim on the inlet trim.
So it would have more lag than the plotted graph suggests if thats the case.
Turbo is not an exact science, the expected can have totally different results.
Just go for it you can change the inlet anyway later if you need to but try it
and see how you go as suggested you never know you might like it.
Some engines on mild boost give better economy than big late boost.
A friend used a t25 from a saab on his 1300cc toyota corolla & went very well,
rpm redline stayed the same yet double the power and very responsive.
His was .48 A/R, 50 Trim, ex. .48 A/R, 60 Trim. with 1.75 su, 2.25 inch outlet.
The saab variable Jmac was talking about didnt come to Australia as far as
I have seen with the turbos if so maybe all done with variable manifolding.

A bit of lag is a good thing mate, can drive around traffic off boost, keep the noise and fuel down then give it some stick and the party starts.

thanks Guys

I went back to my turbo mate and challenged him with your comments Dave.
His response was pretty good.

He said doesnt matter what people say will work, I was referring to inefficiency. He then said its easy to prove, an engine has a max CFM which you can then plot against a compressor map.

We calc'd it using something along the lines of
CFM = RPM x CID/3456 divided by VE

(was last night over the phone so cant remember the exact numbers)
I do remember we used 1.4 liter engine @ 7000rpm and around 80% effiency

That resulted in around 250 CFM

he then plotted on a GT2560R, 60 comp ar and .6 rear

looked like this




I then sent through some of the dyno pics from other turbo A series off the site.

What do you know, if you look at them for about the first 4000 RPM there graphs are almost like a non turbo, then BAM

To tell the truth it was that long ago I can't remember :)

Look up the wiki between differences of H89 (closed chamber) which is superior head for performance to the H75 (open chamber)- Higher comp engines have been successful with bigger turbo on 6-8lbs boost so the A14 should with a .6X rear housing by the sounds of it since Nicks setup cam nicely at 2600rpm. Nick what was you front housing? You probably should go for the 1.75 inch SU or Stromberg for more fuel and air to feed the sucker as TopGear has done in the past and others, one in a datsun 1000 wagon is pushing 30psi with 1.75 inch SU and crude water injection which blew his boxes apart then upgrade to Escort 2ltr pinto 4 speed box cut and shut bellhousing and now the toyota T50.

A14 pistons are a little thicker up the top than the A15 pistons so a little more strength while rings are all pretty thick strong items for all A series.

A friend of mine is pretty turbo savvy. He has played around with a lot of them on 4wds.
He is convinced that this turbo is too way too big and a waste of time. He thinks I'd be better off using something off say a Charade turbo or TX3 laser. He simply said a old 1.4 wont have enough exhaust gas to drive a turbo off a modern 2L. Logical argument...

I've been thinking about how to reply to this all day.
Without wishing to insult your friend even considering a turbo off a Charade shows to me that he really doesn't quite grasp just how much air/ fuel these little motors actually flow.
As I said before I actually ended up using the biggest T2 available off an 1800SSS Bluebird and that was still too small. That started spooling seriously at about 2800 and would rev through to 7500 no problems.
Considering the Japs are renowned for putting too smaller turbos on cars I honestly think that you should have a leap of faith and just try what you've got.
Remember too that your application is vastly different from some-one with a 4wd, so what if it boosts a little late. The thrust back in the seat as you watch the speedo climb and grab gears some would say is better than sex and you'll more than pick it up in the top end!
Interesting what Sikyne is saying about the exhaust manifold. My experience using a 'J' has been really good but if anyone would know Simon is the man.
8lbs boost, sensible spark and correctly fueled and you will have a great little powerplant. Go make it happen and remember plenty of pics so we can follow your journey.

Cheers
Dave

superfatto what was your T25 front AR

your talk about the H75 head made me wonder what is on my A14.

I just checked, its a H89.

what does this mean? I see in wiki thats most likely a B310 A14?

will this be better for this bigger turbo?