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.

S: Car backfires after light throttle is applied and then applied soon after. It also backfires when boosting and letting off – it experiences rich condition and it starts to dip rpm. Sometimes it goes so low that it stalls.

** ONGOING: STILL WORKING ON RESOLVING THE ISSUE **

Observation / Tests:
-BOV is recirculated.
-New distributor was put in.
-The distance between maf and compressor is now over 15 inches (air tight extension was put in).
-IACV was replaced & spare one was cleaned & installed. On first start it blew lots of smoke (hard to tell if blue or black at night) – probably from KA-T#1 (maybe had some oil in it). I will check if it still throws a code.

-If SAFC is setup to subtract more fuel near the idle rpm, car doesn’t dip as much / backfire because (my guess) as it passes that rpm and slows down, the reduced maf signal causes injector pulse to decrease and not much fuel is dumped in. So technically the DEC-AIR function would work here except that doesn’t solve the original problem – it would only serve as a band aid solution. Let’s find the real cause…

-Determining whether fpr had broken down and car sucked fuel via vacuum diaphraghm, I unplugged it – started the car – revved it – appeared to have no leakage from the vacuum line. I went for a ride and discovered it had backfire even after I retuned it.

To be tested:
-INJECTORS: FPR appears to have been fine with vacuum line unplugged, so it could be injectors.
-FUEL PUMP?
-MAF? or MAF in/out setting on safc (It appears that it hits lean right before it backfires, I will try 2 in 6 out and subtract fuel)?

Valve cover painting is one of my favorite diy’s.  Granted it’s nothing fancy like powder coating, it still adds something cool to the unique setup.  I try to make each valve cover bit different from the other.

To clean, prepare & paint a valve cover expect to spend good 7-8 hours of mostly wait time and about 1.5-2 hours of actual work… Ensure you get about 3 coats of paint with some breaks between for each stage.

Let’s start…

1. Clean up the valve cover using degreaser, 400 grit paper, steel brush if needed – avoid creating scratches.

Afterwards wash degreaser off with water, dry it or blow out with air gun.  Tape off the cover top openings to prevent overspray from getting in (follow the shape of the oil cap).

2. Use vaseline to mark off areas you don’t want painted, such as lettering.

3. Use filler/primer to spray the cover – hopefully wet-sandable – if you spot uneven surfaces, use wet sandpaper to smooth it out. If you can’t find filler-primer combo, extra oversprays with some time out can help to make surface even. Afterwards let it dry.
 

4. Spray it with your high-temperature favorite color – in this case I chose orangy-red (lol tang? I am not good with color naming).

5. For the 3d feel / effect, I used mesh – ensure it’s tight (can use elastics) to give you good spread out pattern.

6. Overspray with another color – this time choose a darker color so that when you remove the mesh, the net effect will create lighter mesh effect.

7. After spraying few layers, leave it for a while with the mesh on.. once it hardens, gently peel the mesh away from surface – you will see the 3d effect and also bottom color will now show up as a grid.

8. Have a favorite sticker you would like to embed into your valve cover? Ensure it is a sticker with a shape – as the shape will transfer to the cover. Gently stick it on.. you can put very little bit of vaseline on the back of the sticker for easy removal. Just ensure that vaseline doesn’t spread over any surface areas or paint won’t grip there.

9. For this step, I’ve decided to create an effect of dark lettering on light background. I’ve measured out and created a spray rectangle over the lettering & sprayed 3 layers (with some time between) over the stickers and anything in that rectangle.

10. Now using exacto knife.. gently peel away the letter stickers..
As for nissan lettering.. Use qtip to rub off the paint – since the vaseline is below the paint, the paint will simply drop off the areas where you applied vaseline.. Use small paint brush to finish off the edges around lettering – it will remove the excess pieces you may have missed.

I found as an added protection – clear coat helps and surprisingly stands temperature well – spray 2-3 times (again with dry time between) – it will add more protection to the paint.

Here is the big shot for upclose…

Click here

And here is another valve cover done using similar but slightly different techniques.

And here they are for comparison…

Click here

And one more gloss-black for the new engine build…

Enjoy!

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…