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Paying for SX

The bolt-on 200SX power gains

by Julian Edgar

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This article was first published in 2003.
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Stefan Graf of Gold Coast performance company ChipTorque has his finger on the buyer pulse. As one of the company's two salespersons, he's on the phone constantly, fielding enquiries from a huge range of potential customers. From people who want to price an exhaust for a Commodore to people wanting to know the results of an intercooler upgrade on a WRX, he answers dozens of questions a day. And, rather unusually, he's able to quote dyno figures to support a lot of what he says. We decided to quiz him on modifying the Nissan 200SX models, from the S14 through to the current S15.

"The first thing that we do on the cars is an exhaust - a full 3-inch off the turbo. We run a 3-inch hi-flow cat, resonator and a 3-inch rear muffler. The [type of] muffler will depend on what sort of noise they're after. The price is AUD$1950 for a fully polished, stainless steel exhaust all the way through with the high-flow cat. In mild steel it's around the $1400 mark, but with HPC coating it comes up to around $1750. On the earlier model 200SX we're seeing 15-20 kilowatts at the wheels improvement - that's with the boost rise of about two pounds that also happens when you fit the exhaust.

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"After that, we do the airfilter. That could be a pod style filter - being a Blitz distributor we sell the Blitz product - or running a cold air feed to the standard box and using a K&N filter or some other high-flow filter. We haven't done a lot of research on the feed to the box but we know that the Blitz pod filter on its own will pick up anywhere between 10-14 kilowatts at the wheels. Boost goes up at the same time - about three-quarters of a pound. So with the exhaust and pod intake you're on about 10.5 - 11 pounds. At this stage that's with no engine management changes.

"When the boost comes up to about 11 pounds, that's generally OK with standard management and running a 98 octane fuel. If you want to go to any more boost than that, then we do specify doing a chip to stop any detonation."

And intercooler upgrades?

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"Again being a Blitz distributor we use the Blitz intercooler kit, which is a good kit. It's $2195 to buy the kit and $2500 fitted. However [to fit the kit] it needs a smaller battery, because they run the pipe through where the battery tray is. Rather than going across the top of the radiator, they go up the driver's side, straight into the throttle body. Obviously it's a lot bigger core [than standard] - 610mm long, 266mm high and 68mm thick.

"There is a pressure drop across the core, but from what we've seen it's not massive. But because you generally get the pressure drop, you have to bring the boost back to the same point - then you get a power increase. People are concerned about lag, but if you actually look at the length of pipe that normally travels across the top of the radiator and back to the throttle body, the new length of pipe isn't that much different.

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"Generally these cars run exceptionally rich through the mid-range and top-end - down into the 10:1 air fuel ratios. Sometimes they can even run richer than that. We pull out fuel and add timing - but there are points in the map as well where timing is pulled out to stop detonation on transitions. We leave the [variable] cam timing standard. That transitional ping in the midrange (it comes out of nowhere; it doesn't ping anywhere else) could be cam timing related, but that's fixed by pulling timing out at that point. We work inside the computer with the motherboard, rather than externally splicing in [an interceptor] and so forth. We have control over rev limits, idle and that sort of thing, whereas [an interceptor] has control over just ignition timing and fuelling.

"We don't necessarily specify an intercooler upgrade before engine management changes - the intercooler is what we do as part of our Stage II kit. We can do exhaust, airfilter, engine management and a boost increase and we're quite happy to put that on the road with decent octane fuel. Without a [new] intercooler, an earlier model will have around the 140kW mark at the wheels - that's from a starting point of anything between 95 and 100 kilowatts. With the intercooler as well you're looking around 155kW - with the intercooler we can run 17 pounds in it. The total bill with everything included would be around AUD$6700.

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"On a standard S15 we see between 100 - 110kW generally - and they also respond a lot better to the mods than the earlier models. With an exhaust you're seeing between 20 - 25kW, with the boost also rising two pounds when you put it on. With the exhaust and also an intake we're seeing between 140 - 145 at the wheels. With intake and exhaust, an intercooler, a boost increase to 15 pounds and the engine management mods to suit that boost, we're seeing between 170-180kW at the wheels.

"Above 15 pounds of boost there is reason to go to an aftermarket blow-off valve, but up until that point we don't deem any reason to go to it - they handle that boost level OK. If someone's going to do an intercooler and run more than 14-15 pounds, then you would look at a blow-off valve. The standard blow-off valve tends to bleed off - it doesn't hold those boost levels. We've seen that happen on a couple of high horsepower ones that we've done.

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"On the high power cars we run aftermarket management - otherwise the airflow meter becomes a restriction. Our chip can accommodate a larger airflow meter but once we get to a certain point we just like to go to an aftermarket management and so take the airflow meter out of the equation completely. But we can use a custom airflow meter - custom piping with the airflow meter sensor dropped in - and another option is using the Z32 [300ZX] airflow meter. That is a pretty straightforward change for us.

"We had an S14 200SX in where the customer had fitted an aftermarket pod filter using a bought adaptor. Now the adaptor bolted on to the correct bolt holes of the airflow meter but it didn't match the opening - it hung over the edge slightly. That car was lean - air/fuel ratios in the fourteens, even getting onto full throttle. So we checked everything else that it could be then we pulled the airfilter off - and the problem was still there - so we went further and pulled the adaptor off - and the car came back to being rich again. It was blocking certain areas of the airflow meter or causing swirling or something along those lines so the meter didn't get a clear read.

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"We have seen it also on WRXs where they have a pod filter mounted on a bent tube that goes down inside the guard. The air travels towards the outside of the bend rather than the inside and sometimes can miss the sensor. I can't say exactly what it does but the sensor doesn't get the correct read - it's excessively lean. You bolt the airfilter directly onto the airflow meter itself without the pipe and it goes back to being rich again."

But what about the durability of 200SX engines where the air/fuel ratios are fine but the power has been increased by a whopping 70-80 per cent?

"The SR20 seems to be a very good package - it generally handles the modifications quite well. We've got SR20's - obviously with different turbo combinations, injectors and so forth - that are making 250kW at the wheels on the standard turbo manifold and standard engine internals. But there's also a lot of guys who have done bigger turbos - and have had to do engine rebuilds. We have got a lot of S14s - going back to '94-'95 - that are still running around with our Stage I or Stage II kits with the 15-17 pounds of boost and are as reliable as the day they drove out in them.

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"But I think excessive boost is a problem. Some people get a bleed valve and put an exhaust on it and they don't understand what detonation is or they don't hear it. On the dyno we use a 'chassis ear' [an electronic listening system] and generally have a second person in the dyno room near the engine bay listening for any detonation. The average person doesn't know what they're listening for. Sometimes they'll say 'My friend runs fifteen pounds so I'll run fifteen pounds as well'. But his friend might have ECU mods already. I think that's a common problem.

"I don't think that there's anything wrong with using a bleed valve - we use a bleed on a large majority of the cars that we increase boost on. But we also have a look at what's going on with the air/fuel. We see quite a lot of early model cars - S13s - where the fuel pump is on its way out. The car is still driving but the fuel flow is not there. Now if this customer were to wind in more boost he's got no idea what air/fuel's doing, whereas if we're putting that bleed valve on it on the dyno we can see what the air/fuel ratio's doing and we can see that that there's a problem - it's lean, and let's find out why it's lean before we even attempt to put the boost up.

"I think bringing the car in [for a dyno run] is the safest way to do it. It's not my way of saying 'bring me your money' or anything like that. I think it's our way of saying 'you've done the right thing, you've gone and bought the right parts - so why not have them set up correctly?' Whether they want to do engine management or not, we still set bleed valves for some customers who want to do mild boost increases and just want to make sure that mixtures are correct and there's no detonation.

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"I haven't seen any major driveline issues but the clutch is something that would [normally] have to be done - I'd say sooner rather than later when you went to a Stage II kit. It depends on how they drive and so forth, but even so with the large increase in power they'll normally turn the standard clutch inside out. For AUD$1000 fitted we do a 2400-pound clamp rate heavy duty clutch that still feels basically standard underneath the foot."

One key area where the potential for engine durability to suffer is in inadequate air filtration. After all, most times more filter flow occurs only because there are bigger holes letting the air through... How does Stef reconcile engine durability with questionable filtration?

"I wouldn't sell a stainless steel Blitz pod filter to someone who lived on a dirt road or who was living in dusty conditions. Street driving - I don't have any real qualms about it. The Japanese have used that filter on numerous vehicles - it's one of the main filters that they use. But that's not Australian conditions. We haven't done filtration tests on it - I expect by how much it flows and the power increase that we get from it that the filtration in dusty areas wouldn't be all that great.

"I think that the 200SX responds better for the modifications than the WRX. I personally like the WRXs myself - the four wheel drive is an attraction for me - but for the power for the money, I think that the 200SX is hard to go past."

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