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Discussion Starter #1 (Edited)
GTV 3.0V6 24v supercharged

Hello folks,

I needed to relax from my JTD tuning for a while so I began to think about concept of supercharged 3.0V6 24v GTV. I will share my knowledge and ideas and would like to hear your opinions and experience. I'm not a petrolhead, so be kind to me :)

At the start I prepared few calculations and plottings ...

3.0V6 24v calculations.jpg

rotrex C30-94 on 3.0V6.jpg

I know the real engine volumetric efficiency differs a little (it's probably higher at the low rev and decreasing with increasing revs), but I remember my friend who told me that max airflow he logged on his GTA was about 640 kg/h, so I think those 600 kg/h between 6500-7000 rpm should be ok here.

I heard the 3.0V6 24v stock engine would cope with 0.5 bar (7 psi) boost quite easily. By rules of 10lb/m airflow per 100HP (or 0.1 kg/s per 120HP) the engine would produce little above 300 HP at such boost level. This job would match Rotrex C30-94 supercharger perfectly.

To (almost) reach such boost figures at redline (bold orange rightmost curve labeled 1:1 130) I would need to gear the supercharger to the crankshaft in ratio 1 to ~1. But that seems to be to me like a huge underestimation of the supercharger, as it will goof off all the time, only increasing torque with increasing revs, making it peaky rather than flat.
So the solution is harder pulley.
If I gear the supercharger in 1:1.444 ratio (90mm pulley), I would reach 0.5 bar boost much sooner (red curve labeled 1:1.444 90). Max supercharger revs (100krpm) woud peak at 7500 engine rpm and 1 bar boost. Or 1.25 bar boost at 6500 engine rpm with 80mm pulley.

The question is how to throttle the boost.

1. By restricting the supercharger inlet - at normal (1 bar absolute) pressure on inlet side, the compressor will produce 2 bar pressure max. To get 1.5 bar max, I would need 0.75 bar (absolute) underpressure on inlet side (so if C30-94 compressor inlet is 61mm dia, airbox inlet should be ~53mm dia); or

2. By capping max boost level by some valve, that would open above requested 1.5 bar pressure (mechanical overpressure/pop off/bypass/whateverthenameis valve or /prefferably/ some solenoid actuator operated by MAP driven electronic boost controller) and vent the overpressure.

The first option is IMHO damaging compressor wheel, the second a bit awkward as it need the vent piping back to the airbox (otherwise it would make fancy "pfssssh" sound anytime over ~4500 rpm) and - and this is more important - the second option will turn crazy the MAF and ECU as the part of metered airfow wouldn't enter the engine.

Any other suggestion of boost control or best practice?
 

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Hi Yan.ko,

Looking for a different challenge ?

In my opinion, it's difficult to have a constant boost with a centrifugal supercharger. It will be much easier with a roots blower.
Ofcourse, in terms of power the best would be a turbocharger, a BB Garrett GT2871R for example. Squadra Tuning applied this unit to several 24v GTV's.
 

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Discussion Starter #4 (Edited)
What DIA is the crank pulley on your 3.0l mate
Hi Andy, according to
pulley.jpg

and 60622945,FIAT 60622945 Crankshaft Belt Pulley for LANCIA,ALFA ROMEO

It is 130mm

Hi Yan.ko,

Looking for a different challenge ?

In my opinion, it's difficult to have a constant boost with a centrifugal supercharger. It will be much easier with a roots blower.
Ofcourse, in terms of power the best would be a turbocharger, a BB Garrett GT2871R for example. Squadra Tuning applied this unit to several 24v GTV's.
Hi Joel, every alfist should own busso engine once and I really like the GTV. I got the chance to buy one for good price. So now it's time to learn something about petrols.
Btw. isn't it a sin to kill busso sound with turbo? :lol: Yep, those roots type supercharges seem to be throttled on the intake but their efficiency is quite low and need a big intercooler.
 

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Discussion Starter #6
I know Andy. That was not the question. That I already draw into the chart. Maybe I should write some legend to the chart

thick black curves show supercharged rpm zones
thin orange lines show simplified hypotetical airflow of 3.0V6 engine at given engine speed (1krpm, 2krpm, ...)
thick orange is supercharger performance for given pulley size (80mm, 90mm, ...)

max C30-94 supercharger speed is 100krpm,
- 80mm pulley is the smallest one which can be used on with engine max speed of 6500rpm
- 90mm pulley is the smallest one which can be used on engine with max speed of 7500rpm
 

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Don't go by the graphs as once it all on the car it will be completely different. If you put a restrictor on the intake of the charger all it will do is limit max boost but you don't need it on the Busso. You will get restriction from your airfilter, intercooler and pipework.
You can't have constant boost with a rotrex because even at 2-3psi in 1st&2nd gear at 3000rpm the wheels will spin up
 

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Discussion Starter #8 (Edited)
The efficiency of the latest four-lobe rotors Eaton TVS series superchargers don't look so bad. Either the performance curve is a way better

eaton R900 on 3.0V6.jpg
 

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Discussion Starter #9 (Edited)
Also C30-74/84 would be sufficient, if I keep stock rpm limiter at 7000rpm ...

rotrex C30-74 on 3.0V6.jpg rotrex C30-84 on 3.0V6.jpg
 

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Discussion Starter #10 (Edited)
Finally at home :)

Next to the bigger sister
 

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Discussion Starter #12
Thanks Dan. Yes, it's equipped with Eibach Pro kit springs.

And again they have the same issue like on my 156 - the rear ones lower more than front.
 

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Thanks Dan. Yes, it's equipped with Eibach Pro kit springs.

And again they have the same issue like on my 156 - the rear ones lower more than front.
A set of Konis sorted that on my GTV.

My opinion the easiest way to control the boost will be to use a blow off valve set at the desired boost. And yes you will have to re-circulate or the MAF will not be happy.
I found that the MAF dies above 0.9bar boost it just cannot keep up with the airflow.
 

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Discussion Starter #14 (Edited)
A set of Konies sorted that on my GTV.
Good to know about those Konis. Will try them too.

My opinion the easiest way to control the boost will be to use a blow off valve set at the desired boost. And yes you will have to re-circulate or the MAF will not be happy.
I'm a bit shy with the continuously recirculated setup @5krpm+
rotrex C30-94 on 3.0V6 recirc.jpg
as fueling depends on load which depends on MAF readings. And I'm not sure about its smoothness (we are talking about recirculating of ~10kg/s @7500rpm). I'm sniffing some deadlock :lol:

I found that the MAF dies above 0.9bar boost it just cannot keep up with the airflow.
Was it with 3.0 MAF or 3.2 one? 3.0 is HFM 5-6.4 family, rated to 640kg/h, while 3.2 is HFM 5-8.5 850kg/h one. From my experience I estimated the 3.0 MAF would be good upto 900kg/h which is just fine for 0.5bar boost at redline. In the worst case I can swap for the 3.2 one and update MAF linearisation map in ECU (as I did it on my JTD already).

Btw which fuel pressure regulator have you used in your setup? I was quite surprised that 3.0V6 has no one from stock (while 2.0V6 has one). I'm thinking about AEM adjustable one, or some unadjustable (at least 3.5bar+) Bosch one. Would like to increase the fuel pressure as much as possible for finest atomization. I'm not sure what pressure can the stock pump deliver @100l/h rate. Would like to get to the at least 5bar fuel pressure as I may not need to upgrade the injectors then.
 

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Sorry I forgot to mention.
Yes I am running a 3.0 maf.
Is your GTV Euro 2 or 3?
 

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The oe pump can reach up to 6bar but life expectancy definitely goes down.
I reverted back to a nice and steady 3bar. With the oe setup you will seldom if ever se more than 2.8 bar on the rail. At high rpm in will actually drop to +/- 2bar. That’s why I changed the system so that the FPR sit in front and all fuel run through the fuel rails.
I also changed to a large Bosch pump in the tank. It is the pump that the old K-jet vw’s used it can push up to 8bar and flow more than enough.
I cannot play with the map like you so still run the oe management with injectors and added 4 Subaru side feed injectors to the boost pipe managed by a standalone system.
According to pressure and rpm input it gradually ad additional fuel above 0.1bar. The injectors can flow an additional 1.8l of fuel if needed.
 

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Discussion Starter #18
Wow, what a rebuild! I seen some of your pictures in other threads, but this thread I missed. Mine build will be definitely poorer compared to your, but almost factory looking.

Is your GTV Euro 2 or 3?
Mine is EUR2 '98 model (1999). These models have standard fuel pressure of 3.5bar.

The oe pump can reach up to 6bar but life expectancy definitely goes down.
I reverted back to a nice and steady 3bar. With the oe setup you will seldom if ever se more than 2.8 bar on the rail. At high rpm in will actually drop to +/- 2bar. That’s why I changed the system so that the FPR sit in front and all fuel run through the fuel rails.
I also changed to a large Bosch pump in the tank. It is the pump that the old K-jet vw’s used it can push up to 8bar and flow more than enough.
I cannot play with the map like you so still run the oe management with injectors and added 4 Subaru side feed injectors to the boost pipe managed by a standalone system.
According to pressure and rpm input it gradually ad additional fuel above 0.1bar. The injectors can flow an additional 1.8l of fuel if needed.
I'll probably need the higher performance pump too, as the stock one is 100 or 120l/h one AFAIK. Those AEM FPR and pump looks like a good combo for very affordable price (so much, that I'm worrying a bit about their quality).
 

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Discussion Starter #19 (Edited)
Slowly gathering some stuff for the GTV season ...
 

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Discussion Starter #20 (Edited)
My '98 model GTV is (unfortunately?) equipped with returnless fuel feed system with fuel pressure regulator incorporated into fuel pump, with no reference to the manifold pressure. It seems to me that that pressure diference has to be calculated by the ECU (probably from the engine load), so at the first stage I'll keep the stock fuel feed system and will try to compensate the fuel-manifold pressure difference at boost in the ECU map.


Btw. has anyone ever tried to upgrade or alter that builtin pressure regulator to give more fuel pressure?
 

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