Which engine/trans would you get: Type S with ATTS or SiR S-Spec with LSD?
as some of you may know, I'm doing a swap into my SH.
Background:
Type S - 220hp, ATTS
SiR S.spec - same engine as Type S (220hp), but no ATTS and an LSD instead
All the plans I had made were for a Type S with ATTS, but the engine just came in to hmotors today and Steve tells me it is actually an SiR S-Spec with an LSD tranny (must be M2Z4). It will obviously come with the intermediate shaft, and Steve says he'll throw in the axles for free. So the SiR will not be more difficult to swap.
Which would you guys pick? A few things: I do not have any plans to build this engine at all; I do not autocross; I need to be able to pass emissions testing in Illinois.
The weight savings will be nice with the SiR S-Spec. But I wonder if I will miss the ATTS I've always had and taken for granted.
Now another dilemma is that given I need to keep things OBDII and therefore use my stock SH USDM ECU, I don't know if I can still use the SH ECU with the SiR S-spec engine. People have repeatedly said the SH ECU is ok with a regular JDM H22A and with a Type S, but how about the SiR S-spec?
the following from an faq (is it reliable?) makes me wonder...
"92-96 Preludes have a P13 ecu. Both in The U.S. and Japan.
97-01 Preludes have a P5P ecu. Both in the U.S. and Japan.
96-2001 Prelude SIR Spec S has a P13 ecu. It is different from the p13 ecus that came in the fourth gen and other jdm preludes however. It's programmed for the factory built head etc etc... "
I know that the JDM Type S ECU is NOT readable by the US scanner, so I doubt that this JDM SiR P13 ECU will be readable by the US OBDII emissions scanner.
A thread from the Toronto Prelude Club, however, contradicts this and states that the SiR ECU is a P5M. It goes on to state that the SiR P5M works better than his USDM P5M ECU:
"usdm..37820-p5m-L05
Jdm(Sir S-spec ) 37820-p5m-013
When my engine swap..I did't change ecu..
Now...It is working greater then useing usdm ecu.."
So to do the SiR swap and be emissions passable I'd have to get a hold of and use an unideal USDM P5M from a base 5g, or use the SiR P5M (with more power?) and not be emissions passable.
Regarding the Type S swap, another FAQ in a honda-tech thread confirms that the USDM SH ECU is the same as the JDM Type S ECU:
"P13 : 93-95 OBD-1 Prelude VTEC
P13 : 1996 OBD-2 Prelude VTEC
P14 : 93-95 OBD-1 Prelude Si non-VTEC
P14 : 1996 OBD-2 Prelude Si non-VTEC
P5M: 97-01 OBD-2 Prelude Base
P5P: 97-01 OBD-2 Type-SH
P5P : 97-01 OBD-2 Prelude Type-S (JDM)
That's right the P5P type-s ecu is indistinguishable from the USDM type-s by code only."
This makes the Type S swap seem the best, since I will be using the right ECU (JDM Type S and USDM SH ECU both P5P) and I'll be emissions passable.
wish someone out there had some knowledge one way or the other that could help me... but i know this level of detail is getting pretty obscure.
unless someone can sway me otherwise, I may have to pass up on this SiR S Spec and wait (however many months) for a Type S to come in since I'm more sure about which ECU will work for my requirements... damn.
if all wiring is changed over to USDM, and oil pump with sensors, distributor, etc to make it full USDM OBDII, is it still possible to run either the SiR ECU or the SH ECU? ie, is the ECU independent of all this stuff and easily swappable?
could I drive all the time with the JDM SiR ECU and then just switch to the USDM SH ECU when it came time for inspection?
If anyone knows an answer to any of these questions, I would greatly appreciate it! If not, if anyone can point me towards a JDM ECU expert that would know that would be great too.
I need to tell Steve at hmotors in the next 24hrs whether I'm taking the SiR or not!!!
I don't know if the ECUs would be easily swappable, but I don't think you could get away with the USDM SH ECU with an S Spec engine due to lack of ATTS. Do they read the OBD2 ECU directly for inspection where you are?
Yes, they plug in directly to the port in the passenger compartment just to make sure that the computer isn't reporting any errors. That's it, no visual inspection or sniffer test.
Regarding compression, according to others who have done the swap, the SH ECU is fine.
Regarding the ATTS, yeah, I'm not sure whether I can use the SH ECU on the S Spec non-ATTS engine. But I do know that (1) there is a separate ATTS ECU and (2) when doing a regular JDM H22A swap into an SH, people just pull the ATTS ECU and can still use the SH ECU on the non-ATTS JDM H22 and it works fine.
This suggests the SH ECU would work with the S Spec, but I just can't be sure.
I know you can use the SH ECU with a non-ATTS engine, but does it return trouble codes during the scan? I don't know if anyone has tried that. There is a com link between the ECU and the ATTS controller.
You sound like you already answered your question, though.
haha, yes, but I need to be 100% sure before forking over $4000!!!
That's a good point, I didn't think of the SH reporting errors due to no ATTS. anyone know?
And even if the car runs with the SH ECU, you're right--what good is it spending extra for the S Spec if it runs at 200hp instead of 220 due to the SH ECU not being optimized for it???
Damnit, I just need to determine this stuff for sure...
Since you already have ATTS and don't plan on modding the car much if any, wait for a Type-S swap. I'd DD with the Type-S ecu for max safety and power, and put the SH ECU in for smog time.
The SH ECU in a non SH car will work fine with no codes once the ATTS ECU module is pulled out. I'd honestly go JDM H22A with the OEM LSD trans and swap everything OBD-II over. It sounds like a pain but it honestly makes the most sense for the best price. You're getting a closed desk higher compression motor with a OEM LSD for the price of a decent rebuild on the SH motor. Then if you want more you can always go OBD-I and ECU tune and know you can swap that SH ECU back when its smog time. Mind you I'm talking from experience here and not theory, its up to you but I really did look at this 10 different ways and it was teh best choice for me.
That's good news that the SH ECU doesn't throw any codes with the regular JDM H22A.
Remind me, did you go from an SH to the JDM H22A? I think I recal that you did... having had ATTS and then losing it, was it a big deal for you? What was it like going from an ATTS car to a non-ATTS/LSD car?
Also, do you know the ECU code for a regular JDM H22A? One last thing we still have not determined is if the SH ECU will work with the S Spec motor, which supposedly has a P5M ECU, which the base 5g uses. Compression difference worries me, but if an SH ECU works ok with an ATTS Type S AND a non-ATTS JDM H22A, then you'd think that it should work with the S Spec.
yeah you can do a search too im sure there are tons of subjects on this. FWIW, i have a quaife in my car so thats what i'm comparing it to, but the functionality of a LSD stays the same.
when i was driving my friends SH, the SH system sure is great around corners but its an odd false sense of security/handling. Since more power goes to the outside wheel, there is a certain point where you can smash the gas in the turn and it will hold harder. however at this point you feel like if you let go, you might lose it. please note i said feel, as i never had the balls to test this on the road.
you also only get the activation of the SH at high throttle and a certain amount of steering input.
that being said, i think a SH prelude could probably turn better than one with a LSD.
the LSD seems much more controllable in all situations and predictable. on top of that, there's launches, wet weather, etc.
__________________
1999 Prelude 2.2 VTi 4WS
I speak fluent typo
i wouldn't waste the $ on the sir or the type s, i'd just get a regular jdm and get the lsd tranny with it.
type s was the biggest waste of $, but for the fact that i can say i have a type s
Why do you say it was a waste?
With the Type S, you get to retain ATTS, which is one of the greatest things about the Prelude. An LSD is an LSD... you can add that to any car, but you cant just install ATTS whenever u like. There have been plenty of debate about LSD vs ATTS, and there is no clear cut winner between the two. One of the reasons why I <3 the Prelude is b/c of the weird technology aspect. Without it, Preludes get a little boring.
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