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Well I had stage 1 with stock exhaust. Gains were ok. Then added OAP and felt no difference really. Then added stage 2 and tweaked the tune via sending logs to tuner, and gains were very apparent after that.
That seems in keeping with what one would expect based on other reports throughout this and other forums. Plus, you have a GTS, so whatever you did experience is more than would be expected from a GT4/Spyder
(Very) modest gains with stage 1 tune.
No difference after adding OAPs to stage 1 tune.
Would expect some logging/further tuning if jumping to stage 2 tune with only aftermarket OAPs (still have OEM headers/cats). Most, if not all, stage 2 tunes built on premise the cats are removed.
At the end of the day, it seems the best 'tune' for the GT4/Spyder is a free-flowing exhaust set up. Squeezing out a few more TQ/HP after that with a tune is a long and pricey climb for a short slide.
That seems in keeping with what one would expect based on other reports throughout this and other forums. Plus, you have a GTS, so whatever you did experience is more than would be expected from a GT4/Spyder
(Very) modest gains with stage 1 tune.
No difference after adding OAPs to stage 1 tune.
Would expect some logging/further tuning if jumping to stage 2 tune with only aftermarket OAPs (still have OEM headers/cats). Most, if not all, stage 2 tunes built on premise the cats are removed.
At the end of the day, it seems the best 'tune' for the GT4/Spyder is a free-flowing exhaust set up. Squeezing out a few more TQ/HP after that with a tune is a long and pricey climb for a short slide.
Avera
Its not just about gains though, it is about driveability. The car is way more responsive on S1 with OE exhaust even.
TBH, on a stock GTS vs stock GT4 I did not notice the -20 crank HP between the 2 after driving back to back. I actually rekon the only difference between the 2 is the 200RPM delta. Would I have gone a tune on a GT4?, absolutely.
Its not just about gains though, it is about driveability. The car is way more responsive on S1 with OE exhaust even.
TBH, on a stock GTS vs stock GT4 I did not notice the -20 crank HP between the 2 after driving back to back. I actually rekon the only difference between the 2 is the 200RPM delta. Would I have gone a tune on a GT4?, absolutely.
I hear the term 'drivability' a lot around these parts and, honestly, have no idea what that means?
Can you elaborate?
You suggest you would get a tune on a GT4. I would never dispute what you would do, however, I do wonder if you would have same view if you got a free-flowing exhaust first? I say that from my own experience.
TBH, on a stock GTS vs stock GT4 I did not notice the -20 crank HP between the 2 after driving back to back. I actually rekon the only difference between the 2 is the 200RPM delta. Would I have gone a tune on a GT4?, absolutely.
Besides the 8000 RPM Redline, the GT cars make max HP 600 RPM higher and the max TQ curve is 300 RPM wider.
Might notice the better breathing up high if you look for it. It’s definitely noticeable between the old 3.8 and 4.0, think the 3.8 in the 981 peaked around 6700.
I hear the term 'drivability' a lot around these parts and, honestly, have no idea what that means?
Can you elaborate?
You suggest you would get a tune on a GT4. I would never dispute what you would do, however, I do wonder if you would have same view if you got a free-flowing exhaust first? I say that from my own experience.
Avera
For me drivability = throttle response paired with eagerness to rev and accelerate. I attribute this largely to changing the AFR's and giving the engine a touch more fuel vs running lean due to emissions regs.
I don't know enough re sport cats etc on these cars to comment. I believe OAP's will give you a touch more HP/Torque, but nothing you'd feel. From my research and what tuners say is heat is the problem in the 4.0. Free flow exhausts can reduce the thermal buildup in the exhaust system and stop the car from pulling ignition timing due to excess heat. But to take full advantage of modified cats & OAP's, you'd likely need to couple it with a tune.
When you change exhaust components such as headers or OAP's, tuning becomes necessary due to the changes in backpressure and the airflow model of the engine. The ECU doesn't "know" that you changed any hardparts and still thinks you are running stock airflow modeling. This is why tuning is needed for parts like this. The car will run correctly and make more power while at it.
With M-Tuner, we give users the ability to switch from Stage 1 to Stage 2, and we don't change for moving to a different stage. You can request these tunes for as many octanes as you wish (91, 93, 100).
For me drivability = throttle response paired with eagerness to rev and accelerate. I attribute this largely to changing the AFR's and giving the engine a touch more fuel vs running lean due to emissions regs.
I don't know enough re sport cats etc on these cars to comment. I believe OAP's will give you a touch more HP/Torque, but nothing you'd feel. From my research and what tuners say is heat is the problem in the 4.0. Free flow exhausts can reduce the thermal buildup in the exhaust system and stop the car from pulling ignition timing due to excess heat. But to take full advantage of modified cats & OAP's, you'd likely need to couple it with a tune.
Thank you for providing me your explanation. I wonder if the improved drivability you observed with a tune is any different than that I experienced with a free-flowing exhaust?
In terms of heat soak, I cannot relate it to a tune and/or aftermarket exhausts because I do not track my car and I have yet to hear of heat soak being a problem on the roadways.
I do recall a Dundon interview where they report their high-flow header/OAPs being setup with a titanium rear box and the rear box literally falling apart due to heat . . . on a TRACK, not the roadways.
When you change exhaust components such as headers or OAP's, tuning becomes necessary due to the changes in backpressure and the airflow model of the engine. The ECU doesn't "know" that you changed any hardparts and still thinks you are running stock airflow modeling. This is why tuning is needed for parts like this. The car will run correctly and make more power while at it.
With M-Tuner, we give users the ability to switch from Stage 1 to Stage 2, and we don't change for moving to a different stage. You can request these tunes for as many octanes as you wish (91, 93, 100).
1. My understanding is the ECU is sophisticated enough to adjust to variables such as changing air-flow (e.g., aftermarket headers/OAPs), ambient temperatures, fuel quality, etc. . . sounds like a statement, but that was a question.
2. Have you ever specifically applied a stage 2 tune to a 718 GT4/Spyder with Dundon headers/OAPs . . . or had a customer do so? I’m curious to know if you have any logs showing (a) the car was not performing optimally after the Dundon components were added, and (b) your stage 2 tune optimized the performance?
I ask these questions because I have been pretty upfront to this point in stating I’m not currently in pursuit of an aftermarket tune BUT I enjoy learning/discussing the topic . . . and, perhaps, I might be swayed at some point to pursue a tune.
If I were to get a tune, I would pursue an M Engineering tune based on everything I’ve learned in various discussions related to aftermarket options.
I’ve directed a lot of questions to you specifically, because these are the matters I’d need to know more about in order to push me over the edge.
I hear the term 'drivability' a lot around these parts and, honestly, have no idea what that means?
Can you elaborate?
You suggest you would get a tune on a GT4. I would never dispute what you would do, however, I do wonder if you would have same view if you got a free-flowing exhaust first? I say that from my own experience.
Avera
I've had the M Engineering tune and JCR Silenced Exhaust on my Spyder for about a year now. When I took the car in for its one-year maintenance a few months ago I removed the tune (under 10 minutes). During the 45 min drive to the dealer the car felt a little sluggish; I had forgotten that I had removed the tune. About half way there I figured it out. So subjectively the tune definitely improves drivability even with an exhaust. At full throttle I think it would be hard to feel a 10-15 HP difference. Whether a tune is worth it or not is an individual decision. Since the tune also locked open the valves with PSE on I saved the expense of a valve controller and installation which helps justify the cost of the tune a bit. I have no regrets and am very happy with both exhaust and tune.
I've had the M Engineering tune and JCR Silenced Exhaust on my Spyder for about a year now. When I took the car in for its one-year maintenance a few months ago I removed the tune (under 10 minutes). During the 45 min drive to the dealer the car felt a little sluggish; I had forgotten that I had removed the tune. About half way there I figured it out. So subjectively the tune definitely improves drivability even with an exhaust. At full throttle I think it would be hard to feel a 10-15 HP difference. Whether a tune is worth it or not is an individual decision. Since the tune also locked open the valves with PSE on I saved the expense of a valve controller and installation which helps justify the cost of the tune a bit. I have no regrets and am very happy with both exhaust and tune.
Thank you for sharing your experience. Sounds like you obtained modest, but satisfactory improvement in your overall driving experience.
By no means dismissing your experience, changing out the rear box does not open things up much, e.g., would not warrant a state 2 tune.
I am specifically interested in stage 2 tune after opening things up with aftermarket headers/OAPs, and as outlined in my prior post (#128).
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11-30-2022, 07:25 PM
