Pre-warning : VERY LONG POST
Hi guys,
I have been researching on matters related to the stock turbo on the ER34 GTT in many forums including this one. I have been looking at very different inputs pertaining to this matter. I have attempted many small DIYs with my ER34 GTT since I got the car last year.
Anyway, a background to the car intake/exhaust setup. Stock ER34 GTT Manual 2000.
- Apexi dual funnel intake
- Apexi N1 3" exhaust. 3" from the turbo downpipe. Unsure of the cat is of a high-flow one or not.
- Stock ecu, turbo, I/C, actuator, solinoid from what I can see.
- Pivot speed meter X (for speed cut removal)
Mod #1 - Hoses change
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- Noticed that the vacumm hose between the solinoid & intake (before turbo inlet) had a crack in the opening.
- Decided to change some hoses to Sard Silicon hoses. Got a couple feet of the 4mm & 6mm spec ones. Noticed that the 4mm is really approx 2mm unexpanded in original state and the 6mm being about 4mm. This was the same for other brands like Samco, HKS.
- Changed the hose between intake (after turbo outlet) to the T connector. Original 6mm -> silicon 6mm (4mm). Also reduce the length of hose by 30%. Did not put in the so-called "restrictors".
- Changed the hose between the T connector to the actuator. Original 6mm -> silicon 6mm (4mm). Also reduce the length of hose by 30%.
- Changed the hose between the T connector and the solinoid. Original 4mm -> silicon 4mm (2mm). Also reduce the length of hose by 30%.
- Changed the hose between the solinoid and the intake (before the turbo inlet). Original 4mm -> silicon 4mm (2mm). Also reduce the length of hose by 30%.
- Changed the hoses between the boost sensor and the intake (Just before the throttle plate area). Original 4mm -> silicon 4mm (2mm). Also reduce the length of hose by 20%. Kept the filter in place.
* Noticed the car does not boost as before. Prior to this the boost would be @ exactly the 0.5kg/mm2 mark (0.49 bar or 7.25psi). Yes I know the standard gauge is not very accurate. After the mod, the boost is @ about 0.4kg/mm2 mark (0.38bar or 5.8 psi ).
Mod 2 - High boost Solinoid Mod
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- After reading this post, decided to do the mod. Found a hazard lights switch from the scrap yard that fits the emply slot in the area where the switch to adjust the headlights angle sits. Yep. perfect fit with the clips and everything. The manufacturer of this switch is NISIN, JAPAN. Unsure of what car it is from. This switch has a built in light. Naturally decided to use the light Wired the mod to the solinoid and the light in parallel. So 12V would be given to both solinoid & light when the earth end is connected. The switch toggles between solinoid-ecu and solinoid-ground with light indication when the circuit is completed. Hence when I turn it on, the light would be on and the solinoid would open allowing air to be bled out. When the switch is off and when the ECU gives the Ground signal, it switch & solinoid will also turn on. According to this post, it only happens past 4500rpm.
The ECU toggling the solinoid to open @ 4500rpm is not true. With my setup, when I tested my car. The ECU gives the ground signal even @ 2200rpms. After a good half hour testing, I realize that whenever the boost exceeds 0 kg/mm2 the ECU opens the solinoid bleeding air to achieve the alleged 7psi. There is really no 2 stage boosting in the ER34.
After that mod, I changed my hoses again.
- Reverted the hose between the T connector and the solinoid. Silicon 4mm (2mm) -> Original 4mm. Kept the length of hose like the silicon 30%.
- Reverted the hose between the solinoid and the intake (before the turbo inlet). Silicon 4mm (2mm) -> Original 4mm. Kept the length of hose like the silicon 30%.
- Inserted the "restrictors" into the 6mm silicon (4mm) hose between intake (after turbo outlet) to the T connector.
Results : I now boost to approximately 0.7 kg/mm2 (0.69 bar or 10.15psi). At the change from 3rd to 4th gear, the boost then goes higher to 0.8kg/mm2 (0.79 bar or 11.6psi). Noticing my switch light, it too lights up way before 4500rpm. It lights up (meaning the solinoid is open) @ about a little before 3000rpm. Toggle my switch on with the solinoid open at all times. Same results.
Conclusion :
#1. The mod does absolutely nothing for R34 or at least my car. The ECU is absolute stock. I am starting to believe that the solinoid opening is triggered by something other than the 4500rpm. Perhaps throttle opening ? There must be some difference for the R34 to produce so much more torque (approx 360Nm @ 3200rpm) as compared to the R33 (approx 280Nm @ 4800rpm). So my switch acts merely as an indicator of when the solinoid is opened.. heh heh. Now, I press it to give me pure psychological performance improvements. Afterall, we need to lie to ourselves every once a while.
#2. The restrictors are there not to restrict boost but to restrict boost pressure from hitting the actuator quickly. It reduces the hose's internal diameter from 6mm to 2mm at 2 points. It's more like speed bumps for boost pressure feed to the actuator. Hence, having the restrictors, you should be able to reach the set boost level faster when you floor it and also have some level of boost increase. If you would change that hose from 6mm to 2mm, your boost would also increase.
#3. If you change the hose to and fro the solinoid to someting smaller than 4mm, your boost will drop as the air bleed would be slower.
Guys, correct me if my understandings are wrong.
P/S: I know the standard boost gauge is inaccurate especially when it is closing to the 1kg/mm2 mark.