Can someone tell me the reason I shouldnt boost an NA ?

There must be some reason that I dont know.

If the compression ratio on an NA is 10.4:1 and the TT is 8.4:1 (or so)

Providing the internal pressure in the combustion chanbers on the NA during compression isnt higher than the TT. ie: you use much lower boost.

Whats the difference ??

Whats the advantage of having lower compression settings in a TT engine providing that the max pressure during compression before ignition is the same?

Some one please explain !!

 

Not exactly sure what you are asking here Graham, but .......

the lower compression on the TT would be for safety & longevity. You could throw a couple of hair dryers on an NA with stock compression but any sort of reasonable boost would put your compession through the roof. Therefore, in order to do it safely you would have to severely limit boost which would severely limit horsepower which kind of defeats the purpose.

Hope this helps.

If you could be a bit more specific with your question, then you might receive some more input.:thumbsup:

 

I will try to explain a bit better

Lets assume that atmosheric pressure is 10 psi.

During normal compression in an NA at the top of the unstroke. Atmospheric pressure has been compressed by about 10 times ready for ignition.(10:1 compression) So lets say for argument sake its at 100psi.

On a TT at the same point if the turbo charger is NOT pumping air into the cylninder it would have compressed it to say 80 psi (8:1 compression)

Now with the turbo working the pressure at that point has been pumped up to say 130 PSI due to the extra air going into the chamber. So the turbo is boosting the cylnider pressure by 50 psi.

Now if I took my NA engine and stuck a turbo on it that gave me 30PSI of boost, then I would have 130 PSI in the cylinder as well.

IS there an issue with doing this I dont understand?

Whats different between the two of them?

 

I know alot of SR20DE's that have had a turbo strapped to 'em!

One of them that I know of was expected to last 10000kms max running 8psi - its since done over 100000kms with boost sometimes set at 19psi (has done 24psi) with a BB T28.

This car also hasn't been babied with drifting its main role in life!


Other SR20DE's that I know of normally have a T25 strapped to them and running max 10psi and I haven't heard of any letting go.

 

OK what if

If I got a set of standard Zed turbos, manifolds and dump pipes.

Left the standard ECU in place and used an aftermarket boost controller. What other issues are there that would stand in my way of bolting them all on?

Boost controllers just control the waste gate opening point dont they?

 

nah if you boost to 30 psi the cylinder pressure

will be more like 400psi using your assumption that the atmospheric pressure is 10 psi and the compression ratio is 10:1...

 

Can you explain that a bit better please

I wasnt using the pressures to say thats what I want to do (they are bullshit figures I made up) I was trying to illustrate what I meant.

Isnt the compression ratio linear ?? is it logarithmic ? I dunno !! :wacko:

If you take for example the Zed turbo. What are the actual cylinder pressures during compression with standard boost?

If you could adjust the level of boost of a turbo on an NA engine to have the same pressure in the compression stroke as the TT. Is there a difference?

 

You can

It all comes down to what type of performance you want, ie whether you want to rely on turbos and higher boost to make a lot of your power, or whether you want the engine itself to intrinsically make power, using turbos to add to that power. The VL Commodore RB30 turbo is probably a good engine to use as an example. In stock form, for its time, it was considered a reasonably high compression motor for a turbo, with a 'small' turbo added. The engine made power because it had a reasonably high comp ratio (and it was 3 litre), and the turbo asisted in making even more power, especially as the revs rose. Driving 'off boost', there was still a reasonable amount of engine power, which made the car smooth and responsive.

I don't see an issue with turboing or supercharging an NA Zed, as long as you don't try to overdo it boost wise, as the static compression ratio of an NA is too high to also add lots of turbo boost.

99% of the aftermarket supercharged Commodores and Falcons on the road run mild boost, and retain the original compression ratio and ecu (but it is reprogrammed)

I'd reckon an NA Zed with a small supercharger would be an interesting beast!

 

It would seem to me that

actually running low boost and high compression with an NA, would be interesting as when your off boost in a TT there is precious little power/torque from the engine till the turbo spools up.

Would I be right to assume that a NA with small boost turbo would maybe be slightly faster off the mark? (without loading up the torque converter first on an auto)

In this case would you be able to use smaller turbos than a normal TT, as the amount of boost would be comparitively smaller? ( ie " cheaper")

 

Re: You can

IS there a supercharger small enough to replace the plenum and fit under the hood of a Zed ?? anyone ?

 

Lots of NA's are already faster off the mark

As they are lighter, have ahigher diff ratio, higher compression and (some) may have less traction issues than a TT.

Once the turbo has spooled (doesn't really take that long), the NA is a goner.

Another intersting thing to try with an NA and TT, is leave both cars in 5th doing 80km/h. Then at the same time floor it! Only turbos can pull away quickly like that! :zlove:

 

i remember.....

an old forum member by the name of massivechicken, who all the oldies here would remember. He had probably one of the nicest NA's on the forum and he investigated the supercharger thing. In the end, he discovered that the only way to fit the supercharger was to lose the a/c compressor. It was also very very expensive and the gains were questionable. Do a search on his name and see what you find.

Actually, I just tried a search on his name and it seems that all the old archived posts are currently not searchable (anything earlier than 2004).

Cheers

 

Yes, you could turbo an NA........

Atmospheric pressure is 14.7psi & that pressure is then multiplied by your compression ratio to give you absolute pressure.

In your NA 14.7 x 10.4 = 152.88 psi in your cylinder
In a TT 14.7 x 8.4 = 123.48 psi in your cylinder (with no boost)

So theoretically, a tt can run approx ¼ bar boost pressure before it has the same cylinder pressure as the NA. eg 14.7 + 3.675 = 18.375 x 8.4 = 154.33 psi in the cylinder.

If you put a turbo on your NA that provided 30psi boost (which is just over 2 bar. OUCH) you would end up with the following;
14.7 + 30 = 44.7 x 10.4 = 464.88 psi in your cylinder.

I think you are forgetting the compression ratio of the motor when you "just add" 30 pound boost to your NA.

Both motors have atmospheric pressure (14.7psi) available to them, the TT adds air pressure on top of this to effectively increase the cubic capacity of the cylinder.

Using those figures, an NA could run turbos providing 1/2 bar boost (7.35psi) & still have cylinder pressure under that of the TT running 1 bar (14.7psi).
i.e NA : 14.7+7.35= 22.05x10.4 = 229.32 psi
TT : 14.7+14.75=29.4x8.4= 246.96 psi

 

Thanks Ian

That is exactly what I wanted to know !!

So can anyone think of any drawbacks to doing this ??

Is the top end of the NA engine any different than a TT, head gasket wize or number of studs etc that would create a weak spot?

The reason I am asking all this, is that I have spent so much money and time on my NA, I dont think I can face doing it all again with another car just to chase 50 kw or so.

The bodywork on my car is really nice and so is the paint job and interior, seems a shame to sell it just to get more power.

If the standard NA engine can do the job with light boost seems that that is the answer. The hardware is available and second hand standard turbos are not too expensive. It is bolt on, so we are not talking big mods.

What do I need electronic wize to make this work? Would a Hitech piggy back computer do the job of remapping fuel and ignition for the turbo OK??

Can someone explain how the boost controller woiuld connect in the system?

 

dont forget you would need the following......

Intercooler or Intercoolers. Keep in mind that the NA has no holes for intercooler plumbing, you would have to drill / cut and modify your radiator support to allow the pipes to pass through.

Also you would need a different front bar to accomodate the intercooler.

Perhaps even a different driveshaft to accomodate more power.....

If you do go ahead with it and works fine, let me know, as the temptation would be too much to resist. But as you, i have devoted lots to my NA and could never part with it so selling it and buying a TT is not an option..

Cheers

 

I actually tried

to see if that halfcut in Sydney for $1350 was still available. Even if the engine ws stuffed, it would have had all the bits I would have needed to do this.

That would be a cheap 50kw. The sucker was gone though. I have no doubt others will come up, just have to keep looking.

 

You can get some really quick times with an NA

I know aguy that has added a Turbo to his NA engine (In his 84 Z31) and has managed to run a 12.237 sec 1/4 mile @122.46mph on street tyres which is pretty damn fast.

 

You would at least need...

A Turbo ECU and Turbo injectors.

 

The dark side will get ya one day

It seems to be getting a lot of people :zlove:

 

its scary isnt it???

I think i'm one of the only "oldies" left with an NA. By oldie I mean I have been on the forum for about 4 years. A lot of my fellow NA'ers of the same time either aren't members anymore or have gotten TT's... Ahh well, I'll keep waving the NA flag. Someone has to be different..

Cheers