I'm still trying to figure out a few things about turbos, and the theory behind them, so I've got a few questions to ask. Some of this is just thinking out loud and trying to see if it makes sense, but tell me if I'm right or not. I might use some wrong terms here cause I'm a bit fick when it comes to cars :)

 

Single turbo on a ZX is presumably difficult because you have to feed the exhaust gases from two sides of the engine to the single turbo inlet. This means that either you mount the turbo in front somehow (and move radiators fans and things to allow this) or can you run different length feeds from the different manifolds sides of the engine and set the turbo to one side?

 

Does running longer feeds to the turbo create more lag or just a pressure drop? Would this pressure drop be the same as you would presumably get from running the output to an intercooler - if so could it be compensated for by mounting the turbo near the intercooler anyway - longer exhaust gas feeds, but shorter intercooler feeds?

 

Do the feeds from the turbo output to the different sides of the engine have to be equal length?

 

Why do most of the TT setups on 300ZXs produce less power than many single turbo setups on other (modified) cars. Is it just lack of room to put a pair of bigger turbos in? Do 2 turbos running parallel create much more power than the same model turbo running on it's own, or is there some other benefit?

 

I've heard about spraying water/nitrous/co2 on to the outside of an intercooler and I understand this concept, but I don;t 100% get water injection. With water injection the water is injected in to the airflow (presumably after the airfilter but before the err... is it the plenum??? I said I was fick when it came to naming parts). I thought water in the engine was bad - or is it just that the quantities are so small that it all evaporates? I haven't seen to many cars in mags and on the various forums that seem to run water injection. Any reason - is there a big downside that I'm not seeing?

 

On a totally different subject - how much difference does the brake booster make and does it have to be before the brake cylinder or can it be after?

 

Any answers appreciated:D

Ill try answer the odd bit and clear some stuff up. :)

 

Single turbo on a ZX is presumably difficult because you have to feed the exhaust gases from two sides of the engine to the single turbo inlet. This means that either you mount the turbo in front somehow (and move radiators fans and things to allow this) or can you run different length feeds from the different manifolds sides of the engine and set the turbo to one side?

 

Basically on a Z u can't/won't get a single turbo (not that im aware of), they tend to be used on cars like supras where u have an inline-6.

 

 

Does running longer feeds to the turbo create more lag or just a pressure drop? Would this pressure drop be the same as you would presumably get from running the output to an intercooler - if so could it be compensated for by mounting the turbo near the intercooler anyway - longer exhaust gas feeds, but shorter intercooler feeds?

 

Longer feeds from the filter to turbo will make little difference. Longer pipes after the turbo will give slightly more lag but once up to pressure it shouldn't make any difference. Wouldnt be a good idea moving the turbo's further forward as you'd have more exhaust manifold under the bonnet which would increase under bonnet temperatures dramatically. You might not realise it but often when flooring it you manifolds will be glowing orange!

 

 

Do the feeds from the turbo output to the different sides of the engine have to be equal length?

 

I won't get into details but it wont matter unless talking big differences.

 

 

Why do most of the TT setups on 300ZXs produce less power than many single turbo setups on other (modified) cars. Is it just lack of room to put a pair of bigger turbos in? Do 2 turbos running parallel create much more power than the same model turbo running on it's own, or is there some other benefit?

 

Firstly i'd say there are plenty of big power Z's. If u've seen many other turbo cars with alot more power i'd mainly put it down to money, ofcourse u have to buy 2 turbos and just about any modifications to a z seem to require the engine out, gets costly! Having enough room is a problem on a z but there are plenty of big turbos out there, like the ones on maccas to do list, which will fit and give big power. 2 turbos in parallel will shift twice as much air as one giving potential for lots of power but ofcourse if u have 1 its usually bigger.

 

 

I've heard about spraying water/nitrous/co2 on to the outside of an intercooler and I understand this concept, but I don;t 100% get water injection. With water injection the water is injected in to the airflow (presumably after the airfilter but before the err... is it the plenum??? I said I was fick when it came to naming parts). I thought water in the engine was bad - or is it just that the quantities are so small that it all evaporates? I haven't seen to many cars in mags and on the various forums that seem to run water injection. Any reason - is there a big downside that I'm not seeing?

 

Water on intercooler will obviously cool it down more just like if ur wet and the winds blowing. Water injection is very effective at lowing the combustion temp. A very fine mist is sprayed in after the intercooler. Firstly, this will cool the hot air slightly. Secondly, when the fuel is injected and burnt, the water will absorb some of the energy lower combustion temps by something like 40C, enough to stop problems like detonation some times. Water in normal rain drop form is very bad in the engine, it replaces the air and when the piston goes up, it cant compress the mixture (u cant compress liquids) and kaboom, one screwed engine.

 

 

On a totally different subject - how much difference does the brake booster make and does it have to be before the brake cylinder or can it be after?

 

Makes a HUUUUGE difference. Its situated between your brake pedal and the master cylinder. Inside it's a vacuum. When u press the pedal air is let in one side and pushes the cylinder, meaning u can stop within a couple of miles, something u wouldnt be able to do ini a heavy Z without it!!

 

 

Hope this helps, dont flame me guys if you think ive got some wrong.

 

Rob :)

Originally posted by gibbon666

Single turbo on a ZX is presumably difficult because you have to feed the exhaust gases from two sides of the engine to the single turbo inlet. This means that either you mount the turbo in front somehow (and move radiators fans and things to allow this) or can you run different length feeds from the different manifolds sides of the engine and set the turbo to one side?

 

The Z31 has the latter setup you talked about... this presents a few issues.

 

1. The pulses will generally be incorrectly tuned which will not provide a steady flow of exhaust gas to the turbine. This can lead to irratic boost control (spiking) and a small amount of lag. However if you spent the time in designing the correct length you will advert this, but this is something that takes Nissan engineers a good solid month or two to find out via testing.

 

2. The different length feeds will cause an inbalance in manifold pressure between the two sides. This will load one bank more than the other and can cause increased bearing loads as a result. The engine also will have funky scavenging all over the powerband due to the different lengths.

 

As for a forward swept manifold design you will run into physical restraints as far as placement goes for the turbo, wastegates, downpipe, etc. However this is an ideal setup for a V-shaped engine running 1 turbocharger.

 

Originally posted by gibbon666

Does running longer feeds to the turbo create more lag or just a pressure drop? Would this pressure drop be the same as you would presumably get from running the output to an intercooler - if so could it be compensated for by mounting the turbo near the intercooler anyway - longer exhaust gas feeds, but shorter intercooler feeds?

 

Longer feeds will lose more velocity and heat than their shorter counterparts which will spool the turbo slower. However longer feeds will flow much better at higher rpm's due to their increased scavenging ability.

 

With a larger set of turbos you will not really be able to percieve a difference in intercooler piping length due to it's fast airflow response once spooled. Generally you feel lag with a smaller turbo due to it's lower airflow, which makes it work harder to fill the space - work takes time, time is lag.

 

Originally posted by gibbon666

Do the feeds from the turbo output to the different sides of the engine have to be equal length?

 

No, but ideally you want them to be near equal length.

 

Originally posted by gibbon666

Why do most of the TT setups on 300ZXs produce less power than many single turbo setups on other (modified) cars. Is it just lack of room to put a pair of bigger turbos in? Do 2 turbos running parallel create much more power than the same model turbo running on it's own, or is there some other benefit?

 

Other cars have other engines. There are SHITLOADS of factors for producing power ranging from how high the ring land is on the piston to the coolant temp. Basically don't compare it to a 2JZGTE or an RB26DETT engine, because they are Apples to Oranges.

 

A single turbo is a better setup IMO, but the Z lacks an inline engine which would easily allow such a mod. But to be honest, strapping on a set of turbos capable of 500bhp on a Z will make it a psychaotically powerful beast.

 

A turbo will flow only X amount of air... if you have two they will flow 2X amount of air... so no, they do not make more power. It is quite simply easier to install two turbos on a V-shaped engine than it is to fab a single turbo setup.

 

Originally posted by gibbon666

I've heard about spraying water/nitrous/co2 on to the outside of an intercooler and I understand this concept, but I don;t 100% get water injection. With water injection the water is injected in to the airflow (presumably after the airfilter but before the err... is it the plenum??? I said I was fick when it came to naming parts). I thought water in the engine was bad - or is it just that the quantities are so small that it all evaporates? I haven't seen to many cars in mags and on the various forums that seem to run water injection. Any reason - is there a big downside that I'm not seeing?

 

It's sprayed in a controlled mist form, which when it reaches the intake port is vaporized fully. Water absorbs heat much faster than air (jump naked out into a 32 degree day and it will take forever for you to die, jump naked into a 32 degree pond and your dead in no time)... so basically it absorbs heat from the intake charge, which as noted can lessen detonation and other mal-aspects.

 

Originally posted by gibbon666

On a totally different subject - how much difference does the brake booster make and does it have to be before the brake cylinder or can it be after?

 

DAY AND NIGHT... you know how hard it is to push in a caliper piston by hand? ... Well multiply that by 4 and now try to do it with your leg all at once. The car will require you to apply all your might onto the brake pedal to slow it.

A turbo will flow only X amount of air... if you have two they will flow 2X amount of air... so no, they do not make more power. It is quite simply easier to install two turbos on a V-shaped engine than it is to fab a single turbo setup.

 

You've lost me there. If you can flow 2X amount of air, does it not mean you can then add more fuel and have more power?

 

 

DAY AND NIGHT... you know how hard it is to push in a caliper piston by hand? ... Well multiply that by 4 and now try to do it with your leg all at once. The car will require you to apply all your might onto the brake pedal to slow it.

 

I only asked this as I saw an unusual Z on TTnet that had a pedal box fitted. This meant that the cylinder was right behind the pedal, along with the reservoir. Does that mean that the brake booster would then be after the cylinder?

Originally posted by gibbon666

You've lost me there. If you can flow 2X amount of air, does it not mean you can then add more fuel and have more power?

 

Yes but the overall design of the engine/pistons limits the kind of power it can safely handle due to the amount of heat produced etc.

Yes you can put bigger turbos on but it will really need forged pistons, different plugs, bigger intercoolers, bigger radiator, different ECU etc etc and by then you have a very different engine to the one you started with.

 

The Z has relatively small turbos (it's like having 2x 1.5L turbo engines bolted together) so they spool up faster than a large single turbo so you get a more responsive car with less lag.

There are single turbo setups on a Z32. Not many because they cost a lot to do.

 

Single turbo setups produce more power than twin turbo because most people dont want to spend the money on 2 huge turbos. If you are going to spend loads of money on doing a powerful setup up its easier and cheaper to buy 1 huge turbo than 2 huge ones.

 

I would like to say that power is not everthing. Get these cars with the huge turbos which produce amazing amounts of power on to a drag strip and they wont do as well as you think. Huge turbos create huge lag.

 

The 300ZX has quite small turbos to reduce the lag. Supra TT has one smaller than the other i believe, where the smaller turbo spins first creating boost lower down the rev range and also help the larger turbo to spool up.

 

Dont forget that the Surpa engine was completey redesigned when the 300ZX came out.

SRRAE has it spot on, the Zed has two smallish turbos of a hybrid design which virtually eliminates lag. They spool up quicker and at lower revs than one large one to give instant acceleration, whereas large turbos need plenty of revs to spin them.

 

The Supra TT has twin sequential turbos. ie one small one to spin up immediately to give no lag and low down power, then the second bigger one cuts in to keep piling on the power once the small one is spent. Hence the 326 bhp and 325 lb/ft of torque on a UK Supra. This is easily installed on a straight-six engine so a similar set up on a Zed could therefore require 4 turbos...........

 

......Now there's an expensive thought.

 

Also remember that it is more down to torque than big BHP which endows a car with good acceleration. Big BHP is more in the interests of top speed

I understand the whole sequential turbo thing - I actually find that easier to understand than the TT setup.

 

Forgetting that the rest of the engine would need upgrading for now - presumably the reason why each of the turbos produces less power is something to do with each only being supplied with half of the exhaust gases, whereas on an Inline 6 all of the exhaust gases are going through one turbo. Is this right? So if I fitted a single XYZ turbo being supplied all of the exhaust gases, it would produce the same power as 2 XYZ turbos each getting half of the exhaust gases? Presumably though the single turbo setup would have the turbo running faster than the twin setup (twice as fast if there were no outside factors)? And as it has to spool up to a faster speed there would be more lag. Have I got this right?