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Discussion Starter #1
I need help!!!!!!.
I intend to mount some forged pistons with comprasion 8:1. My intended boost will be around 1.5Bar.My question is: How much I can inrease the stock capacity using the actual cilynder(just using the bore procedure)and what kind of pistons and what brand I can use .:confused:
(75engine 3.0 v6 12v year 1989 or 164engine 3.0 12v 1992-I have both)
10x all:rolleyes:
 

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You can bore the stock liners .040" over. I like to bore them .010" over. The displacement increase in either case is virtually insignificant but the .010" number results in a stronger liner and it's an easy number to work with.

I have 8.8:1 non interference forged Venolias. I can have them made as 8.0:1 as well.

Greg Gordon,
www.hiperformancestore.com
 

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Why would you want to go with such low compression? The pistons that greg sells would be ideal. Very low compression is an old school of thought. With many advancements in aftermarket efi. A higher compression can be run.
 

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Chelo, good point, but with 22 pounds of boost (about 1.5 bar) I think 8:1 and good ignition timing probably would be better than 8.8:1 and having to retard the timing. That's really just a guess as I have not done any work above 10psi. However I will soon.

Greg
 

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water injection and 8.5:1 :D Add room for an extra liter of coolant and quart of oil to help keep temps down ;)

Chelo, good point, but with 22 pounds of boost (about 1.5 bar) I think 8:1 and good ignition timing probably would be better than 8.8:1 and having to retard the timing. That's really just a guess as I have not done any work above 10psi. However I will soon.

Greg
How far are you pushing the bar this time? :)






Get it, bar? :D I couldn't resist.
 

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Discussion Starter #6
First of all my concern is detonation and lower gas octane on the pump (in my country).For this reason I think is easy for me to compress the air at 22 psi and after cool down (with water-methanol injection and large intercooler). If I chose a higher compression ratio I can't interfere inside the engine during the compression and detonation in this case can occur.

Chelo=> you right that low compression is an old school but the detonation don't ask what efi you have :p .In some happy situation efi can rich your mixture , inject some water ,retard your advance and put some power limitation BUT AFTER detonation is detected .If you want to avoid someone try to not face him!! For this reason I will try to avoid first "mechanically" and after that supervise with efi.
My ECU know: 2 wide band lambda(I use 1), 2 EGT(I use 1) ,2 knock sensors ,boost control,6 injectors, 6 coils,water injection control,anti lag(I will not use),map,tps,mat,crank&cam hall,stepper motor for idle,and my favorite shift-cut function. IS NOT MOUNTED YET.

Also I intend to use: oil cooler with electrical external pump and at the end if is possible oil squirters for each piston(I don't know yet if I can fix some small pipes under the crank)

This is my first big project and any suggestion is welcome. 10x All
 

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What form of forced induction are you using, turbo or supercharger?
There are some excellent examples of people using high static compression ratios and high boost pressure here in Australia.
The first example is a turbo kit for our LS1/2 (Chevrolet) powered Holden Commodores where 11psi has been fead into an engine with a 10.9:1 (LS2)compression ratio with the engine running 98 octane fuel.
The second example is a Toyota 4AGZE (factory supercharged 1.6ltr 4) running a big turbo (supercharger removed) pumping 30psi into an 8.9:1 compression ratio on 98 octane fuel.
Supercharger/turbo charger and intercooler choices are just as important as selecting a quality engine management system and having a quality tune programmed into it.
 

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As far as detonation goes, I really agree with K_gpz on this. The drop from 8.8:1 down to 8:1 will keep the motor farther from detonation under boost. I have looked very closely at the cars running huge amounts of boost and high static compression ratios and in almost every case they are either running race fuel, very little timing or both. Very often they also have engines that were designed from the factory with forced induction.

Another thing to consider is that there is no knock sensor out there that will work with the 12 valve Alfa so it's really important to avoid knock in the first place. I am a strong advocate of water injection. If your engine management system has provisions for knock control it can be connected to the water injection system so that when the water level is low it retards the timing. (I have not actually done this, I go another route)

The logic behind the 8.8:1 compression ratio I designed is this:
1. We can get in enough boost to blow the transaxle with these pistons so we don't need any lower. (original SuperVerde ran 7.5psi, no intercooler, no water injection, L-Jet and 89 (r+m/2) pump gasoline. Not even premium fuel!)
2. With the supercharger removed or when off boost, power is very close to stock (drag race verified!). The off boost issue is important because I don't want the supercharger to engage every time I encounter an minor uphill section of the road. With a turbo, you have essentially the same issue.

With all that said, I would really be uncomfy with 8.8:1 and 22 pounds of boost on an Alfa V6 with pump gasoline.

Greg Gordon,
www.hiperformancestore.com
 

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Running 22 lbs of boost with what turbo? Many things have to be considered with turbos. For example. In my turbo truck i have gone as much as 24lbs with a 20g mitsu turbo. It starts getting out of effieciency at that point. I have an 8:5 compression ratio. Without boost the thing is a slug. The gt35r will make as much power with only 17~18lbs.
Power can be made with higher compression as well. Just run lower boost. The later being the prefered method of many engine builders. It also gives you much better linear power. It does not come on real hard.
 

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driveline!

what about the running gear?
what are you thinking of running to rear wheels hp?
you want to get your rear gearbox sorted out,also the dounuts,those famous donuts(not the kk)every time you launch or go hard on the pedal there goes the donuts.
you want to find out what hp you can run through the driveline. first before you go to hard on the motor.;)
 

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what about the running gear?
what are you thinking of running to rear wheels hp?
you want to get your rear gearbox sorted out,also the dounuts,those famous donuts(not the kk)every time you launch or go hard on the pedal there goes the donuts.
you want to find out what hp you can run through the driveline. first before you go to hard on the motor.;)
If you're popping doughnuts then I'd recomend reading Greg Gordons article.
http://www.hiperformancestore.com/guiboDSclutch.htm
Also, lots of very torquey Australian cars like the BA XR6 turbo (450Nm torrque), FPV F6 Typhoon (500Nm torque) and the LS1 powered Commodores have a rubber doughnut in their tailshafts, so if they survive (obviously they're not the same 'brand' of doughnut) in those heavier and more powerful cars, then they should survive in a lighter, less powerful Alfa 75 so long as things are properly aligned.
 

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Discussion Starter #13
what about the running gear?
what are you thinking of running to rear wheels hp?
you want to get your rear gearbox sorted out,also the dounuts,those famous donuts(not the kk)every time you launch or go hard on the pedal there goes the donuts.
you want to find out what hp you can run through the driveline. first before you go to hard on the motor.;)
The car have almost 200hp now .From my calculation the car will have around 320Hp (limit for stock conroads ) The gearbox on 75 is very solid one(it's oversized like on most quality car from that age).From other project I found that gearbox can handle around 400hp without failure.(was a site cmosengeneering or something like that with one 75 biturbo around 400hp without any upgrade on driveline)
It is true , I'm concern for clutch(I intend to use ECU shift-cut function) and LSD
 

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Discussion Starter #14
What form of forced induction are you using, turbo or supercharger?
There are some excellent examples of people using high static compression ratios and high boost pressure here in Australia.
The first example is a turbo kit for our LS1/2 (Chevrolet) powered Holden Commodores where 11psi has been fead into an engine with a 10.9:1 (LS2)compression ratio with the engine running 98 octane fuel.
The second example is a Toyota 4AGZE (factory supercharged 1.6ltr 4) running a big turbo (supercharger removed) pumping 30psi into an 8.9:1 compression ratio on 98 octane fuel.
Supercharger/turbo charger and intercooler choices are just as important as selecting a quality engine management system and having a quality tune programmed into it.
I intend to use one gt28Rs .I will run again my calculation for 8.4:1 -8.5:1 compression and I will try to keep the BMEP under 300psi (20.6BAR 5yearplan unit:)).Also maybe you have the guaranty for 98octane in Australia I will consider 95 octane even I pay for 98.:(
Chelo have right it's a compromise between lover rpm torque(under 1800rpm) and max power .Will see I'm little bit dizzy now.
 

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what I wanted to say was that a single gt28rs is a undersized for a 3 liter engine. you can get much greater power at a lower pressure with a bigger turbo. However, two of those are actually oversized. You just have to compare the engine flow to the compressor map and see how it works out.
 

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Haven't done the actual math , but if you want 1.5bars better look at 2 of those :eek:
I think one would do it, but it would be at the high end of its surge limit. I would recommend a GT30. You won't lose any lag time and it won't be running at a higher load, like the 28. My $.02
 

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I think one would do it, but it would be at the high end of its surge limit. I would recommend a GT30. You won't lose any lag time and it won't be running at a higher load, like the 28. My $.02
You are almost right .When I start this project was like:"just a little boost with stock pistons" after that I decide to change the pistons and my new GT28R with 28RS(200$extra) .AND NOW GT30:eek:
I think the smaller one will cover more rpm interval. The big one(gt 30)will have a better efficiency. HMMM .Here you have a both compressor maps gt28R and GT28Rs with some plotted points for 3.0 12v .I think I cover the engine with 28Rs.

Nikoror =>"compare the engine flow to the compressor map and see how it works out" -this was done in first place.
 

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