Choosing the right turbo for me in my stage three project

Now my turbo is in midland turbos hands and im waiting for them to get back to me im looking into the kind of spec ill be running and looking into what turbos will suit my needs.
Thankfully ive had exsperience in the past with turbos and turbo tech aswell as a course at turbo techniques so bare with me!!

What ever turbo i choose i aim to run 1 bar of boost 14.7psi (15psi set at normally) and i need a compressor wheel and housing that will flow enough air at that given boost to make around 150 plus bhp.

on a compressor map you have to plot two lines, one is the pressure ratio and one is air flow in lb/min or CFM.
here is a very rough idea off the flow requirments needed without going into it to deep -

P/R = (14.7+15)/14.7 = roughly 2 P/R

CFM equals = litres x rpm x V.E x P/R

my CFM = 1.25 x 6500 x 85 x 2/5660 = 244cfm/14.27 = 17 lb/min required airflow!

Bare with me if its slightly wrong as ive not had to do this in a while so ive worked it out on paper first haha.

so i need a compressor that will flow roughly 17lb/min of air at a pressure ratio of 2.

If i dial these figures into the compressor map for my GT15 turbo as i have now it goes of the map at the choke line with 210,000rpm!!, this is why my turbo superheats the boost and causes huge losses!

But also i need a turbo that will flow half the max lb/min at half the revs without surging -

17lbmin/2 = 8.5lb/min air flow at a pressure ratio of 2, @ 3250rpm

ill post when i have had alook at some compressor maps to see what suits my engine best at this given airflow but these results are based on a V.E off 85%, 6500 rpm max and running 15 psi so i will play around with the figures

jason

Right im back, ive been researching all day................

This comes down to me needing a turbo to flow at least 15-17lb/min at a pressure ratio off 2 on a compressor map.

But on looking into this my hybrid idea may not be so peachy......yes by hybriding it i could acheive the right flow rate and make more power and torque but it looks like my T15454 is going to cause a problem at 135bhp plus because the small 0.35 a/r turbine housing is just to small for higher outputs

Im going to have to bite the bullet and go for a full new turbo!
using the figures i dialed into the compressor map for my own turbo ive found a perfect turbo for my requirments-

Its called the Garrett GT17 (GT1752) turbo from the saab 9-3 and 9-5 2 litre turbo petrol, dialing in my flow and pressure requirments on the map for the GT17 shows it to be running at its most efficient point on the compressor map making it the absoulute perfect turbo for my engine, in turn this will deliver the most power and torque possible for my desired 15psi.

Problem is there pricey, but they are proving extremly good on the mini 1275 turbo engines achieveing 150bhp at as little as 0.65 bar (10psi ish) and as high as 184bhp @ 15psi, its a far more modern turbo than mine or the T2 and the T2 has roughly the same turbine a/r as the GT15 anyway plus the T2 doesnt like to run boost as high as 15psi without superheating the charge temps and the compressor housing a/r is only 0.35 anyway.
So im going to have a word with the guys at midlands tomorow to see what they have

jason

Latest update on the turbo issue -

I spoke to Midland Turbo's today after waiting all day for them to ring which meant i new there was gonna be bad news!
They have stripped down my turbo and found that the turbine wheel is badly pitted due to heat transfer from over reving, the turbine housing is cracked and the shaft is worn and heat damaged from the over reving again.
He told me its showing all the signs of needing a bigger turbo as i already new

I pitched my idea of the GT1752 turbo to him from the calculations i made above and he agreed it would be an absoulute perfect turbo for my engine at my requird boost level, so im ringing him back tomorow to see what trim compressor wheel choice will be best and also to see which turbine housing will fit best seen as i will have to modifiy the down pipe etc.
Im thinking its now a wise desision to go ahead with the engine swap while its off road and get it all sorted properly once and for all.

jason

Hi everyone, here is the latest update of issues, problems and a checklist!

the car is sat in works lock up looking sorry for itself and turboless! ive yet to hear from Andy at Midland Turbo's but the last time we spoke we decided the GT1752 turbo was the way to go......it comes form the Saab 2 litre turbo engines and its perfect opertaing range is between 150bhp220bhp upto a max 250bhp depending which compressor wheel trim and size you go for, for my spec i would imagine he will advise me to go for the 55 trim compressor from the 150bhp Saab 9-5, this will be ideal for the flow requirments for my spec!
But in order to fit the GT17 turbo to my engine things must change a fair bit because my current plumbing is for the GT15. So the first thing i have to plan is where in relation to my old turbo the new one will sit and to fit it in the first place a new manifold adaptor plate to bolt the turbo to the manifold.....i plan to use a second manifold to do this so i can have a T15 manifold spair
Once the turbo is attached to the manifold in such a way that it doesnt foul on anything then i have to get Hawleys top welder to make me a new down pipe, i believe the new turbo's exhaust housing has a circle flair flange so it shouldnt be to bad to make a new down pipe up for it
There is also a few things i need to ask about the turbo too such as is it watercooled? and does the compressor outlet face up or down?? at the moment it doesnt matter as im totaly blank as to which way will be best for me.......if the outlet faces down the intercooler pipes will be be better layed out with less overall piping and bends, but on the other hand if the outlet faces up (like it did before) then im better off trying to move the radiator to the other side off the car and mounting the intercooler on the O/S like this -


Either way im gonna have a hard time fitting the new bad boy blower

But i WILL get the new blower mounted up ready for the road.........the big desission is do i go ahead and get the engine stripped out yet or not? here are my plans and options -

Im going to buy a punto 75 1242cc MPI 8v engine and a 1242 16v engine.....the pistons and rods from the 16v will then go into the 75 block giving me a low compression bottom end that is lighter and stronger than my current one and it will benifit from new piston rings and main bearings etc.

I have a punto 75 cylinder head in the garage that has been ported on the inlet ports and as standard the 75 head has bigger inlet valves and ports than mine anyway along with 4 injectors! so ill pop new seals in that head and port the inlet manifold to match the head......

Thats my basic engine plan........

But i also have a J and S Ultra Safegaurd waiting for me which is an active knock control ECU which uses a knock sensor to listen for DET,,when DET is detected it retards the timming and then re-advances it until DET returns etc etc. this means the engine is protected against meltdown from DET! The J and S also has a boost input so you can set it to retard timming when the turbo hits the required level off pressure where DET accours.
By fitting this it also means a slightly higher C/R can be run which again gives more power and torque and makes the engine more efficient.

Buuuuuuuut my other plan is to get the turbo back, stick it on, whip my decompression plate off and use the J and S to run it up at the rolling road.
Doing this will still gives shed loads more power then current and will allow me to run the car while i build the new engine up.

i will update tomorow when ive spoke to Midlands..............

jason

Right......just came off the phone with Midlands to descuss the turbo, the good news is the T15/T2/T25/GT17 and the GT20 all use the same centre housing (some are water cooled some earnt) so they can use my housing and fit the GT17 Saab turbine housing and turbine wheel, and the small trim GT17 compressor wheel and housing making it A GT17 hybrid with a GT15 bearing housing

Ive had a word with the Exhaust lad next door and he can make me a flaired flange down pipe with a holding flange that im getting from Saab.
The manifold adaptor plate should be straight forward to make as i have a gasket coming from Midlands as a template
Ive opted for the compressor outlet to face down (opposite to how it was before) so that i can have a far far better intercooler pipe route with less bends in it.........

ill post with some pics of the new Hybrid GT17 blower when i get it......probably friday is.

thanks

jason

Abit more good news, firstly the GT17 Hybrid is £330 plus vat which is really good! but i rang Saab up today to get a clamp to clamp up the new turbo to the new down pipe whre i spoke to a very helpful guy who uses a Saab 2.0litre turbo in his cavalier! and he has a down pipe and clamp that i can have for nothing result!! he is dropping the stuff of tomorow dinner time........yeeees!

But the main good news is ive paid for my new J and S Ultra safegaurd ignition controller which is being posted first thing in the morning. I can fit the controller to the car asap and remove the decomp plate giving me higher compression and better bhp/torque ontop off the Hybrid turbo!
Ill get it set up like this and then build up the new engine in the meantime.

thanks

jason

Richard from Saab dropped of the GT17 down pipe flange today and a manifold - turbo gasket so i could use the gasket as a template to make the new main flange to weld to the new manifold, Sav next door has welded the new flange to my old mandral bend downpipe ready for the new turbo and ive started work on the exhaust manifold flange, see pics below -

This is the old maifold and flange for the GT15 i used before



And here is the new flange im making for the GT1752 Hybrid -


this is the flange with the gasket that i used for a template


This is the new and old manifold with new GT17 down pipe/flange


New down pipe and the old GT15 flange on the left -




Tomorow i will be drilling out the centre of the new manifold flange ready for the turbo and ill be chopping up my new manifold to weld the flange to

thanks

jason

Here is my new cylinder head which i will use to go to MPI, the inlet ports heave been ported heavily and the head has been powdercoated red, i will be porting the exhaust ports and manifold to match before it goes on!




thanks

jason

Jason,

Good news on the Turbo, you might want to think about moving the rad to the other side anyway (this is where the aircon heat exchangers are mounted (I think Arc moved his rad to the NS), it would give you loads of room to do a shorter pipe run for the intercooler or you could maybe even fit a bigger one (as you are going the saab route the 93 intercooler is a nice size)

you might want to be careful when removing the Decomp plate, the J&S will retard on knock but you really want to avoid knock in the first place. you may end up retarding too much to avoid knock that the car ends up slower and your EGT's will go through the roof cooking your lambda sensor. Also if you are close to the edge and hit knock for example when giving it beans overtaking you may find the loss of power resulting from the J&S actively retarding the ignition on a knock event could give a trouser filling moment

If you want to run high boost and high compression without forged internals you really need something like water injection to keep the thing in one piece, you can make up a diy kit quite reasonably and you will be surprised how much more head room on power that would give you

I'm still intrigued to know how you plan on transferring the power to the road though, you know the problems I was having with mine running silly boost

Martin

thanks martin, id be removing the decomp plate and using a stock head with two gakets for a very short period before the new engine is built, i dont think i mensioned that before, then the C/R will be 8.5:1 rather than mid 7s as it is now thats all, so i shouldnt get any of those problems anyway running the cooler charge temps from the new turbo

thanks

Also martin ill be ringing you to have a chat about the settings for the J and S for m engine because it has come today

jason

Im looking forwards to seeing the differnce with the GT1752 turbo, after doing all the reasearch on it its become so obvious that its the perfect turbo for the 1242 engine if your looking to for 150 plus bhp, the A/R of the comp housing is 0.53 (much bigger than a T2 turbo) and the exhsut housing is much bigger than the T15 without being to big to spoil drivability (0.47), the mini turbo guys said they are getting 4psi at just 2400ish rpm so its still coming in early, plus the fact that they have hybrided it with the GT15 bearing housing means its an easy fitment back on the car. Result

jason

I stopped behind to finish a few things up today, ive finished making my new manifold flange and its a great fit to the new turbo..............which arrived today

Its an monster compared to the GT15 before, the A/R of the turbine housing is 0.47 (old one was a tiny 0.35) and the compressor housing has an A/R of 0.53 (old one was 0.33) so its a big bugger for the 1242 engine but its perfect for my requirments.
Also the new J&S Ultrasafegaurd came today too all pics below -

J&S safegaurd ignition controler -



My new GT17 manifold flange i made today -



And finaly my new GT1752 Hybrid turbo........and me nursing the new blower aswell haha

Hmmmmm shiny turbo

Just in case anyone wants more info on the J&S especially you Scooby guys look here

Martin can you link me to the page i need on the website for a wiring diagram?? its me being stupid i still cant find it! thanks

jason

1250cinqturbo (ADMIN) wrote:Martin can you link me to the page i need on the website for a wiring diagram?? its me being stupid i still cant find it! thanks

jason

look here http://www.jandssafeguard.com/MiataInstall.html on the 2 channel mode

im not sure how this works, according to that wiring diagram i only use the input form a cam sensor (which as you no i dont have) and this uses the single wire knock sensor as with the kit i had before??
And there si no boost input on this one. does my setup not requir both in out 1-2 ports to be used for both coil packs??

thanks

jason

This is my idea on how i thought it might be wired up -

MAP - in out = no use on my car??

IN 1-2 = coil 1 negative and coil 2 negative

OUT 1-2 = coil 1 neg to ECU and coil 2 to ECU

GND = earth

12V = live

KNK = two wires to knock sensor

TPS = not needed??

TP = not needed

Boost input from manifold.

anywhere near martin??

thanks

jason



jason

No you need the 2 channel mode, look again it will make more sense

Give me a shout I can go through it with you as the instructions are crap and it takes some working out. Also the how to set up/tune are in the archive section

allanhelen wrote:No you need the 2 channel mode, look again it will make more sense

ahh abit better -



but........this shows a duel igniter!? i see better now but i still dont under stand which wires from my coil packs go to which ports on the in 1-2 out 1-2 connector?? it takes a little understanding with it not being exactly for a cinq set up.
Im still assuming the neg side of the coils go through the J&S??

soon as i no how to wire it ill pop it on

thanks

jason

The instructions are a bit confusing
Here is the link to the Miata wiring diagram http://www.madracki.com/miata/images/wiring/00sys.pdf it is the BRN & BRN/YEL that are tapped into on the Miata which to me looks like the coils are triggered on the earth, iirc the cinq is also triggered on the earth so I reckon you are right

MAP in out is basically a FCD so you don't need it

You just tap into the knock line so leave the knock sense connected and tap into the signal line from he knock sensor

the TP is the test point when you are doing on boost retard if you look at THESE instructions I know it is a different version but it tells you how to set it up