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Discussion Starter #1
2002 Chevy Tracker ZR2 4x4 4DR 2.5L

I'm in the middle of swapping out my Suzuki H25a (2.5) for a Suzuki H27a (2.7) as described in a separate post, and I'm not sure which fuel injectors to install.

The 02 Chevy 2.5L uses the same H25a engine found in the Suzuki Grand Vitara.

Suzuki offers the following part numbers:
For the 2.5L injectors: 15710-67D00.
For the 2.7L injectors: 15710-52D00

I've been unable to find out the differences between these two. I did learn (according to Amazon at least) that they do not interchange, and neither do the seal kits.

Per some advice I received elsewhere, I'm trying to use as many parts from the 2.5 when reassembling the fuel delivery system for the 2.7 - intake, fuel rail, sensors, injectors and so forth. I'm stumped whether to try to fit the 2.7 injectors onto the 2.5 intake and fuel rail, or if that's even possible.

Am I at risk of running lean with the 2.5 injectors? Or somehow starving the engine of fuel?

Can anyone point me in the right direction for making this decision? Should I be looking at fuel pressure? Flow rate of the injectors? Both? Anything else?

There are also some differences between intake manifolds and TBs for the 2 engines so they also don't appear to be interchangeable. At least not without some difficulty.

I posted a similar question on the XL-7 1G community, and so far no response.

Any advice appreciated.
 

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I would guess that the 2.5 injectors would be ok, with the caveat that your fuel trims may run higher. Just a guess though.

Please take plenty of pics, and if possible show us the differences between the two motors. Certainly would be handy down the road for the next guy. Who knows, I might be that next guy!

Sent from my Moto E (4) Plus using Tapatalk
 

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Discussion Starter #3
The diameter of the injector bore is 15.7mm for both intakes. The injectors may have different specs but I don't know why the seal kit doesn't interchange.

I'll try to post some photos tomorrow.
 

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Discussion Starter #4
Same question as mine addressed here:

He had both injectors flow tested with the follow results:

2.7 WHITE 30sec test 65cc
2.5 GREEN TOP 30 Sec test 75cc

This seems counter intuitive to me, but ok.

Also he says:

DONT FIT WHITE INJECTORES TO H25A unless you are using the complete 2.7 efi unit ecu and all
The length you just use the correct fuel rail to match the injectors

Likewise ok with me, since I'm not swapping the ecu. I'll just have to keep my fingers crossed on the fuel mixture.
 

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Discussion Starter #5
Here are a few photos that compare the two intakes and associated components - 2.5 v 2.7.

First obvious difference is in the throttle body. The one for the XL7 (2.7) looks smaller to me.
Second, the injectors, described above.
Third, look at the front crossover pipe or plenum or whatever it's called. The 2.7 has some part attached to the left side that doesn't appear on the 2.5. Probably the most significant distinction.
And there are miscellaneous other differences.

Next I'll post some comparison photos of the injectors themselves.
 

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Discussion Starter #6
The white injector is for the 2.7 / XL7. The green one is a stock injector for the 2.5. Note the different dimensions.

Edit: a little explanation. The first 2 are a pair of photos showing the different pintle diameters. The second 2 show the length of the injectors themselves. The third 2 show the height of the injectors as installed on the fuel rail.
 

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Discussion Starter #7
The photos of the pintle diameter may explain why the injector seal kits don't interchange. The white injector has a larger pintle diameter than the green one. Which means the collars must have a larger diameter, too.

Bad news: For some reason I ordered the XL7 gasket kit. I think at one time I intended to install the XL7 (white) injectors; however now I've decided to install the green ones. (Altho most of the gaskets do interchange, there are some obvious differences. Also the injector o rings and seats appear to be interchangeable, but not the collars.)
Good news: The seller screwed up and sent me 5 seats and 7 collars, rather than 6 and 6. So I get to re-order.
 

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Third, look at the front crossover pipe or plenum or whatever it's called. The 2.7 has some part attached to the left side that doesn't appear on the 2.5. Probably the most significant distinction.
That looks like the mainifold length changer on the left hand side, its a butterfly thats vacuum controlled and opens and closes to change the manifold length to increase bottom end power.
 

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Discussion Starter #9
That looks like the mainifold length changer on the left hand side, its a butterfly thats vacuum controlled and opens and closes to change the manifold length to increase bottom end power.
Interesting. I looked this up and I guess it's also called variable intake runner length or variable intake tuning or similar.

Considering the power curve I just looked at, I'm considering adapting that 2.7 changer to the 2.5 manifold. I don't remember the vacuum setup but I'll figure it out.

You think it will throw a curve to the 2.5 ECU?
 

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I'm guessing your 2.7 is from a 2003+ model year? My '02 doesn't have the variable intake mechanism. Thanks for taking the time to document!
 

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You think it will throw a curve to the 2.5 ECU?


I think there's a VSV (Vacuum Switching Valve) attached to that tank (#26), if I'm correct, the 2.5 ECU will not have the "smarts" or the connections to control it.
 

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Discussion Starter #12
I'm guessing your 2.7 is from a 2003+ model year?
Yes, sorry, it's a XL-7 2004 model year, USA spec I would assume. I got it from a guy who bought it from a junkyard so I don't know much about it.
 

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Discussion Starter #13
I think there's a VSV (Vacuum Switching Valve) attached to that tank (#26), if I'm correct, the 2.5 ECU will not have the "smarts" or the connections to control it.
Thanks. I looked at the tank and the VSV last night after my post and yes, thats how it looked to me too. Plus there's no sensor on it. This would be a nice horsepower bonus.

I'll look into it further and report back.
 

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Maybe wire it with a toggle switch on the dash - try it open/closed at low rpm and see which gives what you want?
 

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Discussion Starter #15
Plus there's no sensor on it.
I think I spoke too soon.

Here's a better diagram of what came with my engine. The vacuum tank (assembly #1) is Suzuki part number 13480-65J00. It has a pinkish Aisin control valve attached to it, p/n 1348A-65J00. Photo attached.

It seems to me, and without knowing more, that the ecu controls the aisin valve according to fuel demand. As the valve opens and closes, the ecu regulates the amount of vacuum pressure necessary to operate the butterfly. Do I have it so far?

Your diagram fordem doesn't show this aisin controller / valve thing. In your diagram, the vacuum hose goes straight from the butterfly assembly to the top of the vacuum tank. No valve in-between. Have you ever seen the setup shown in your diagram - the vacuum controlled assembly without the electronic valve?

I'm still checking which intake components I'd have to swap over, in order to take advantage of this. I believe if I use the 2.7 intake, I could bypass the aisin valve and rig up the assembly shown as #26 in your diagram. Do you think it would work?
 

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Discussion Starter #16
Maybe wire it with a toggle switch on the dash
I looked closer at your diagram and yes there does appear to be an Aisin style solenoid valve on it, too. So yes I suppose I could control it manually.

Is there a down-side to just bypassing the solenoid valve? Or the tank for that matter?

The tank - is it just a filter?
 

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Consider the tank to be a vacuum reservoir - it "stores" a vacuum so the butterfly valve can be actuated even when the/if the intake manifold doesn't have enough vacuum when the VSV is activated.

I don't know how/when the system is activated, but, it's going to be an on/off type deal - open the butterfly above (or below) x00 rpm - or maybe open it between x00 & y00 rpm. You're going to get to tell us it works better with the valve open at high rpm, or it works better with the valve open at low rpm.
 

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the manifold is longer for better bottom end, so its open at low revs, and closes about 3500 ish on the 2.4's at least, not sure on the V6 models, but it does the same job, changes the inlet manifold length and the standing wave pulses in it as well.


heres some brain frying info on the subject ripped from one of my tuning books

<snip>.....

Long runners take advantage of the intake charge velocity to ram air into the cylinder, superfilling it at low RPM.

The long runner and narrow cross section required to get this effect is a detriment to HIGH RPM air flow needs. EFI enabled a medium combination of both worlds with a larger cross section runner because there were no issues with fuel fall out, as fuel is only added at the last instant before the air charge enters the head. This is/was also facilitated with the compound bends in the EFI runner. If someone attempted to do the same thing with a carb application you end up with a 20" tall tunnel ram sticking out the hood.

The V engine dual plane runner intakes were an attempt to increase charge velocity, but would have a few issues with fuel fall out and carbon deposits in low speed eddy areas.

Because of the limit of length with carburetors the harmonic wave tuning was done to a 6th or even 8th harmonic, for a given RPM. With long runner EFI manifolds its actually at the 4th harmonic, so you see a much greater result.

another interesting tidbit, the harmonic tune is not static, it is dynamic, and the RPM of affect is actually a floating wave, depending on atmospheric pressure/intake runner pressure. It is the speed of sound, that is used for the added push, and its noticeable on some engine builds where you see several torque/HP bulges. On blown cars where there is significant boost pressure in the manifold, that sonic wave is slowed considerably, there may actually be an ability to use a 3rd harmonic instead of the 4th due to the slower speed of travel.
 

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Discussion Starter #19
the manifold is longer for better bottom end
I don't understand. What does "long" mean in this context?

The manifold length is cut shorter when the butterfly closes?
 

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Discussion Starter #20
The "long" intake runner effect on bottom end hp is achieved by the expansion chambers. This runner length effect however is a detriment to fuel demand at high rpm air flow needs. That's what I'm reading.

So the short version is, the butterfly valve eliminates the "long runner" advantage at high rpms. Is that about right?
 
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