Ken-chan's car blog

This page shows my T25 rebuild assuming you took the turbo apart (you can just see how it’s being put on and reverse the steps)…

http://www.makemilk.com/pic_hosting/s1495/diy/t25_rebuild/

S: On a hot day, you start to lose brakes after boosting for a while.  Brake pedal will get spongy and start to travel closer and closer to the floor as if there was a leak somewhere in the brake lines.  Brakes come back to normal operation few hours later once car is cool again.

C: Very likely problem with Master Brake Cylinder heating up. 

Here is what happens – usually occurs with boost past 9 psi.   Please note that ballpark measurements over time were taken with infra red meter.  With car boosting a lot especially during hot weather, manifold on T25 can reach close to 280 degrees C and on the underside of the turbo near wastegate / turbine close to 380 degrees (tested on non-water cooled t25). 

As long as you are driving, the flow of air through the engine bay will keep the air moving preventing the hot parts impacting the Master Brake Cylinder (MBC).  The problem often occurs once car stops and is either turned off or sits idling for a while – about 10 minutes later, you start car, drive off but notice the brakes are really weak and travel further to the floor.  What happened was that due to the lack of moving air through the engine bay – the manifold and turbo started cooking your mbc – I’ve seen temperatures close to 98 degrees C on the MBC housing and 110 on strut bar above.  Then when you let car sit for few hours, brakes return to normal operation once temperature of the MBC cools.   I haven’t looked into why exactly the problem occurs inside the MBC – from looks of it oil rises towards top of MBC plastic container and seems like less oil / lubrication is available in the actual cylinder – if you push pedal on hot MBC, you can hear bit of scraping and lots of pedal travel indicates there is just no oil in the cylinder when you push on it.

I noticed that anytime the MBC housing reaches over 65 degrees, you will start to see degraded braking performance such as spongy pedal, etc.

Solution: Make a brake heat shield & replace fluid in MBC with synthetic fluid.  Issue went away for me just by heat wrapping the MBC & just draining fluid from mbc & refilling with synthetic dot 4 fluid.

A quick generic tool to help pick tuning settings based on throttle / hi / lo points…

http://www.makemilk.com/pic_hosting/s1495/diy/safc2_install/safc2.xls

There was a nissan advisory somewhere on removing the top & 2nd chain guide for ka24de since they used to wear and cause damage when they broke into pieces and fell further into parts under timing cover.

Here’s a quick diagram on what to get rid of.  For that you just remove top valve cover (12 m10 bolts from what I remember) and few more m10/12 bolts to remove top timing cover to get to the 2nd chain tensioner.

Remove the old gasket material and reseal with fresh gasket maker seal (I use the copper type – about $7).

One way to increase boost without using the spring is to partially block the boost line going to the actuator – thereby preventing the boost from pushing on the wastegate actuator – that is how many boost controllers do it. Please be careful when using this technique as boost can rise to max out the turbo if you close off too much flow for the boost line.

To manually set your level of boost, you could either buy expensive manual boost controller or opt out for simple industrial 1/4″ npt 2 port valve which will run you about 1/4th the price of the fancy brand name boost regulator.

Example of manual boost controller that I use…

Please note that Line L1 (boost source reference line) can use one of several sources:

• nipple on turbo housing (it is a factory feature on some turbos)
• nipple on the cold side intercooler piping
• nipple on the hot side intercooler piping
• intake manifold vacuum lines

Line L2 leads to the wastegate actuator (operating an internal or external wastegate).

Please note that there are many forum debates about which boost reference source solution is best to avoid boost spikes.  In this article, we’re just covering the idea for a basic DIY manual boost controller.

This type of valve will handle typically in the range of 100-150 psi so there’s no need to worry about failure due to pressure, but it is important to get the fittings tight & snug to prevent leaks.  The cost for this type of “boost controller” is about 6-7 dollars.

One way to test your boost would be to use pressure gauge and air compressor – if you don’t have either or both – for starters you could blow through it with your mouth and see where the closing point for flow is.. once you find it.. open it up a bit to limit the flow about 1/4 of the way. Then try boosting gently (not just dumping gas and seeing where it hits). If your turbo didn’t gain anything, you must close it up bit more and try again. Once you find the sweet spot on the valve regulator based on the boost level you enjoy, mark position of the regulator knob on the valve – this will help you find it easier in the future should you find reason to change it.

Based on bunch of useful articles I found on the web – I’ve done the wheel swap..

http://www.makemilk.com/wtb/mods/wiring.JPG

Horn connection inside…

One of the horn signals is conducted back through the mass…

http://www.makemilk.com/wtb/mods/wheel_swap1.JPG

http://www.makemilk.com/wtb/mods/wheel_swap2.JPG

If there’s enough interest, I might add some more details on it – but there’s plenty of coverage about that on zilvia where I found one of the articles on there.

You can download free copy of conzult software and buy a circuit board which interfaces directly to your nissan consult port via your laptop…  It shows bunch of useful real time parameters such as timing, coolant temperature, maf sensor voltage, etc.

Easy to plug in…

Works with new & old laptops – if your laptop has only usb ports – just get $12 usb-to-rs232 (db9) converter.

Close up…

How to use relays inside your car…

Anybody that uses safc for a while may notice that knock values rise with temperature outside, especially with sun out.  There are debates on how accurate the knock reading is – I think it’s alright – it did pick up some values when it run lean for for me so I added extra fuel and it’s been sitting at 0 (calibrated) so that’s good.  As far as extreme knock values - some of it is due to hotter running motor but a lot of it has to due with the fact that SAFC 2 doesn’t do so well in the sun or heat blowing at it from the air vents.

In the picture above, I calibrated my knock already and it was showing value over 200 - my motor should have been shaking and choking – and it was pretty smooth.  At first I was concerned about the knock level until I noticed how hot it got on the black bezel behind it in the sun.  Since then – I’ve tested couple of more things to be sure – but yes – safc 2 (at least the knock value) is affected by the hot air.  If I place safc 2 near vent and turn on some warm air, my knock level goes from 0 to about 10-15.  In the direct sun, I got over 200 that time — so before you guys panic about your motor — make sure your safc is cool.

Ok guys – I run into this before with a friend who’s plug broke off wires near the nissan 240sx MAF plug and he needed something to work for him for few days.  Yeah it’s got scent of ghetto but it works..  It probably will work with other ones as well – it sits tight as well.  It’s your standard power supply plug for EIDE devices.. cut off the plug with some length of wires and then just solder or splice.
Just make sure to tape off the back of it so it’s bit more moisture proof.

 http://www.makemilk.com/pic_hosting/s1495/diy/temp_broken_maf_plug/broken_maf_plug_tmpsol.jpg