8v 2l Twin Charged -my Little Project - Alfa Romeo Bulletin Board & Forums

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post #1 of 1227 (permalink) Old 05-06-2008, 05:04 AM Thread Starter
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8v 2l Twin Charged -my Little Project

Thought I would pull my finger out and post up some porgress on my twin charged project.

If people are interested I will add more detail as I go. I actually have been writing a doc to cover what I have been doing so I can prob cut and paste bits.

Outline:
Aim
So the aim of this project I am setting out on is to increase horsepower…but why? What do I want the car to do? The 1.8l Alfetta is slow by todays standards, and so I would like to bring it into the 21st century…and then some. It will be predominantly a once in a while street car (probably around 2000km’s per year), but may see the odd track day in the future. So what are the main things I want to achieve then?

1. The car must retain standard lines (no guard pumping etc)
2. The car must be able to be returned to original condition with minimal fuss
3. The conversion must be cost effective without appearing cheap.
4. The horsepower target will be 300 rwhp on pump fuel.
5. Fuel efficiency is important, but due to small distance driving – not the be all and end all.
6. The horsepower must be obtained without engine family change (No twin-spark of other makers engines allowed)
7. The package must be reliable, no point having a dyno queen.
8. Lots of low down torque.
9. It must be a challenge, I like a challenge!
10. It must be street drivable and tractable



Hardware chosen to achieve requirements:
So with the constraints I laid out for myself, a few things became clear. The engine should remain an 8v engine as to keep with the beautiful Alfa design which aesthetically is hard to beat.. It would require forced induction of some description and for reliability and tractability it would probably require fuel injection.
The engine chosen was a late model 8v 2L engine, going with the adage that you can’t beat cubic capacity.
This left me with the decision of what type of forced induction to use to obtain the desired hp. I must admit I ruled out nitrous oxide on the basis that it’s not remotely road legal to have it hooked up….and there's no challenge in it. Next up is turbo charging, but with the 300rwhp target, I worried that the engine would have excessive lag for that instant tractable hp for ‘out of corner fun’. In fact I know this to be the case from past builds I have completed...even with rollerbearing turbos. On the other hand, supercharging tends to become inefficient at the upper rpm range if low down grunt is to be maintained, also the lack of variable boost for roots type chargers is a problem as compromises inevitably creep in. I could have used a vortex supercharger rather than positive displacement charging, but I would still have the issue of lack of low down torque.

I figure a feasible solution would be to supercharge the lower rpm band and turbo charge the upper rpm band. This would give the best of both worlds, low down torque for that small V8 feel, and the satisfying upper rpm surge that turbo’s are renowned for. Best of all, it would be a challenge, actually my mind was made up when I was told I’d been smoking something and it would never work.

So that was it, I was going to build a 300rwhp 2l 8v Alfetta GT with twin charging via roots supercharging and turbo charging.

Existing twin charge examples:
Delta S4 turbo boosts supercharger, then bypasses supercharger), twin stage intercooling
Mazda March super turbo (turbo boosts supercharger till about 3500rpm, then switches to turbo only)
Voltswagon Golf 2007 (turbo boosts supercharger till about 3500rpm, then switches to turbo only
2004 SPI Mini cooper S twin charged (300rwhp claimed)
Stock Eaton Supercharger with Stock Pulley and Garrett Turbo.

Method or forced induction
After reviewing various methods of twin charging from manufacturers and various individuals around the world, I decided on a method.

I plan to pressurise the supercharger inlet with the turbo charger. The turbo charger stage will be intercooled. The turbo will be sized to provide 350 rwhp at 6500rpm at approx 23psi.

I would LOVE to twin stage intercool, but packaging space is at a premium. This will limit max boost allowable, but given my very low comp ratio, I suspect that I will still be able to run 15psi, which is ample.

OK, so for a few photos of the proposed setup - dummy fitted in the shed with modified manifold bolted up.

Enjoy
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post #2 of 1227 (permalink) Old 05-06-2008, 08:22 AM
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This is an exciting project. Lancia had a great deal of success with this twin charging method. So did Alfa Romeo, although in that case they used a Roots supercharger blowing into another Roots supercharger.

A couple things, Roots superchargers are not inefficient at high RPM. At one time they were inefficient at high boost levels but that's becoming less and less true all the time. If you have any doubts, watch the video I post here showing a second gear pull. Notice the rate of acceleration does not drop off at high rpm. You should also notice the low discharge temps on the red digital gauge (outside air temp was about 65F). Adjustable boost is easy to set up on a Roots blower, although the boost control system on a turbocharger is somewhat more efficient.

In any case, I do think your design will give a best of both worlds situation and I am really excited about it.

Video:

Greg,
hiperformancestore.com

P.S.
If you need crank pulleys to drive that supercharger, I have them in stock.

Last edited by Greg Gordon; 05-06-2008 at 08:24 AM.
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post #3 of 1227 (permalink) Old 05-06-2008, 03:55 PM
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I would have thought blowing into the turbo would have been the better way to do it, set it up with a Reed Valve so that the turbo can pull from atmosphere when it outstrips what the Blower can supply?

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post #4 of 1227 (permalink) Old 05-06-2008, 08:08 PM Thread Starter
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Thanks for the interest guys, feedback is welcome and desired.

To rebut a couple of things. I take your point that roots superchargers are getting better efficiency wise, but the supercharger I am useing is an SC14 supercharger from a 2L toyota straight six. It's capabilities are well known, and I can assure you that the effiency drops with the combinatino of high boost and high rpm. So I reason that my relatively high boost requirement of 12psi balanced out with my low rpm expctation will keep me in a range where an acceptable level of heat is generated. remeber I am not intercooling the second stage (post supercharger) so have to be very carefull with outlet temps here.

Whilst roots superchargers are gerat and give excellent results, and new ones are improving, there will ultimately be a compromise to make when searching for 350hp out of a Alfa 2l motor. To size it suitably, I'd end up with a higher power draw from the charger, and a choice to be made about where the best efficency should lie....with this setup, I have two efficiency isalnds to take advantage of...meaning...hopefully an improved efficeny zone over all. It will improve fuel effiency....and hey, lets face it....I want a challenge and it will be that in spades.....I also LOVE turbos :-)

I did consider boosting the turbo, there are a number of reasons that I did not do it this way, mainly packaging. It will work just fine the way I have laid it out and there is no additional complexity with respect to the valving.

Cheers
Mike
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post #5 of 1227 (permalink) Old 05-06-2008, 08:19 PM
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Buzzed: I think having a BIG turbo fed off of an appropriate sized supercharger to eliminate lag would make more sense, but to each their own. Have you done/are you planning any motor mods? Also, have you thought about water injection to help keep temps and knock down? Looking forward to see more progress.

Greg Do you have any more clips like that. It was great, but too short

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post #6 of 1227 (permalink) Old 05-07-2008, 05:16 AM Thread Starter
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5yearplan:
What you actually suggest would not really eliminate lag. For starters, lets call lag the time an engine takes to make boost (I know I'm twisting it a little but stay with me)......I will have boost from about 1500rpm with the roots supercharger....with the additional bonus of greater mass flow through the engine due to the charging from the supercharger. This will infact help to make my relatively large turbo (not the one in the photo, but a GT3071R) spool up as though the engine were a larger displacment engine.

OK, so perhaps you were refering to the schrgr helping to spool the turbo as it passes through the intake....it really doesn't, the blades are not designed to deliver shaft power, the turbine blades are, but intake is not. You can do it...theres plenty of tractor pull vehicles with series turbo chargers, but its not for spooling, its for peak boost.

In fact, I really dont mind too much how much lag the turbo has....except for one reason, I want good transient response of the turbo and heres why:

1500 to 4500 - supercharger makes 12psi
3500 to 4500 - turbo will prob make around 10psi - total=22psi
At 4500 supercharger ius disengaged, and heres the trick in my opinion, the turbo has to replace that 10psi as quickly as possible, or it will appear as though the engine has lost power momentarily. This is why I have chosen a roller bearing turbo, and this is why I have a rather special bypass valve (thats my little secret for now...cuase its not flushed out totally yet)

So good question, but I am convinced this is the better way in my case to boost the engine. Its a packaging thing as well, theres more room on the lhs for intake etc.

And my final challenge is this....if it was good enough for lancia delta S4 groupB, Mazda March and the golf, then it's good enough for me :-)...and Ican tell you, the Lancia delta s4 used a BIG turbo...try 700+hp
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post #7 of 1227 (permalink) Old 05-07-2008, 06:51 AM
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Ah, I think I understand you now. It's too bad you couldn't use an STS style turbo setup where the turbo is at the rear of the car, as it would probably give you the room to intercool both stages. I would look into water injecting the supercharger stage to keep temps down. I am interested in how you will be able to smooth the transition from turbo to charger... Also, are you planning to use an atmospheric vent blow-off valve, or route internally. The second option would give you better response. In my old supercharged car, I could tell when the charger had reached the end of it's efficiency. I could feel the Hp curve drop off a bit above 5500 rpm as the boost maxed out at 14psi. It would have been nice to have had a turbo that would "spool" at around 4000 rpm to develop another 5 psi at 5500 rpm, extending the Hp curve into the redline. It was most noticeable in 5th gear, when I maxed the car out at 145 mph, because the last 15 mph I could tell the supercharger could only barely keep up. I will note however that I had no business going that fast anyway, but I was curious as to what the car could do. Back on topic, I understand that your build is quite different in that you have 2L approx. of displacement where this car had 3.6, a lower redline and weighed quite a bit [and you have much less room under the hood]; so a bit of an apples to oranges comparison. How much does the alfetta weigh anyway? Also, where did you source the Toyota supercharger from, I am looking for a charger for an 2.2 liter. A very cool project indeed.

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Last edited by 5yearplan; 05-07-2008 at 07:05 AM.
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post #8 of 1227 (permalink) Old 05-07-2008, 02:49 PM
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If you use a roots type and run the turbo in to it and Do Not disengaged it works out very very well. The turbo will push the roots so the load goes to 0 or even negitave(the roots is adding power to the belt).

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post #9 of 1227 (permalink) Old 05-07-2008, 07:09 PM Thread Starter
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slyalfa - wouldn't the restriction of the supercharger be too great and actually act as a restrictor in the line? Also, it still absorbes power from the system to drive the mass...and gives me the issue of overspeeding the charger.
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post #10 of 1227 (permalink) Old 05-07-2008, 07:13 PM Thread Starter
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5yr plan:

the supercharger was purchased from the web...be carefull not to get the sc12 (they are shorter) as they pump 1.2liters per rev vs the sc14...which is 1.4liters as the name suggests. It comes off a toyota straight six motor..the name evades be at the moment.
They cost between 350-450 depending on condition and parts supplied...try to get the pulley, switches etc and ensure the clutch works.

Actually I have a spare one...I may sell it at some point if someone needs one.
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post #11 of 1227 (permalink) Old 05-07-2008, 07:33 PM
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Cool, I will poke around the web and see what I can find. I'm not ready to get one yet, as I have enough projects right now... By the way, what size injectors are you planning on using? Will the stock fuel/ignition system keep up?

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post #12 of 1227 (permalink) Old 05-07-2008, 08:20 PM
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I like what your doing. I'm a huge fan of boost. Tell me a bit more about the offset of the wheels. The stance on the alfetta looks absolutely amazing. I love the deep dish rear wheels. What are the wheel widths? Any other pictures of the car? Are those Simmons wheels?
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post #13 of 1227 (permalink) Old 05-08-2008, 06:30 AM Thread Starter
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Hi guys,

heres a few answers to some of peoples questions

Find fault as much as you like, it can only serve to help the end product.

The scharger outlet will be cut and shut to point forward and go between the belts. Actually there is room to bend it back if need be anyway.

As for room for turbo, this setup as it sits came out of a rhd alfetta and fits fine, its actually an autodelta exhst manifold, has a part number on it from Alfa, with an adaptor to point the turbo forward.

Intercooler is air to air and is custom to fit in the front...actually I got it off an Alfa that had already supercharged his alfa...so again, it fits nicely.

Fuel part...camira inlet manifold, rx7 s5 fuel injectors (550cc), bosch factory computer and crank angle sensor...fully programmable, lada niva coils/crank sensor, and the coild I could not get anymore with the ignitor, so I got them NOS from a cavalier I think it was. Lots of old GM stuff used the same setup.

I have all the parts sitting in the shed....granted it does not run yet, so I wont get too cocky...but I am quietly confident.

See attached for wheel offset: (and if you need more info, I have a doc I can send you with a tyre calculator that I made and a 'max' tyre combo that I reckon would fit under the guard). Please note that it looks as though my alfetta guard had been flared ina past life slightly.
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File Type: xls Alfetta simmons tyre suize fitted.xls (22.0 KB, 480 views)
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post #14 of 1227 (permalink) Old 05-08-2008, 06:54 AM Thread Starter
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oh and if you are not familiar with simmons, then you should know that they make custom wheels to your specs...they take about 7-14weeks to manufacture after your order is placed and these wheels cost about 700 per corner, less tyres.

I actually had to drop the 245 tyre back to 215 on the rear to pull the overall diamter down, as it sat too high in the rear, ideally as it sits now, I would lower it 1inch more in the rear as the car sits at standard heigh currently....but I am suspicious someone has cranked it round one notch in the front on the torsion bars. It has not scub lock to lock, but its sagged a litte on the drivers side wchih means it does bruch the tyre when turning in the car park...I plan to fix this with new front suspension...one day!
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post #15 of 1227 (permalink) Old 05-08-2008, 02:58 PM
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buzzed, you mentioned making your own monoblock. My guess unless you have a great computerized milling machine it might take a bit of time. I exchanged a few emails with the fellow (can't think of his name right now) who makes them in Australia. Some years ago I also exchanged a number of emails with Jim Steck (in the US) and I mentioned this monoblock since Jim was in the process of making his own for the Bonneville TS. Jim felt there were inherent flaws in the Australian design and designed his as a combination of girdle and monoblock. Jim sent me the first photo after 12 hours of straight milling. The second is of the competed work of art.

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