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Random question for those of you who have dynod I have stock intakes with high flow filters, catless downpipes, and tuned by weistec. Car makes 550whp at 5.25k rpm but by 7k rpm it’s dropping off to nearly 450. I’ve seen some dyno charts from aftermarket intakes that seem to fix this issue. Anyone else have a similar issue on stock? Would aftermarket intake seriously make this big of a difference on the top end? For example, this is modalworks dyno vs mine
Stock turbos are too small to make more power at the top end. It's why pure software tunes pretty much just increase low and mid range torque/power. You need bigger turbos if you wanna make more power at the top.
*****You sure the car isn't running out of fuel at the higher RPM's ??? Do you have AFR or EGT data as well? The power at 5.25k seems spot on from your description of mods but it IS odd to have so much drop off at the higher RPM in my experience. I just had my car in for some dyno testing on Friday including intake testing versus stock, and a few other knick knacks to verify the car is healthy for bigger mods (much bigger turbos, blah blah), as well as to verify I have enough fuel up top, look at fuel trims, if there's timing retard, knock, etc..
Anyway, yea. It seems kind of odd in your case from the graph you show. How many miles on the car, and do you have either AFR or EGT data up top? Or even a decent scan tool log showing timing being pulled or knock, etc..? Any chance the spark plugs are loading up or your coils crapping out or experiencing higher RPM breakup?
*****You sure the car isn't running out of fuel at the higher RPM's ??? Do you have AFR or EGT data as well? The power at 5.25k seems spot on from your description of mods but it IS odd to have so much drop off at the higher RPM in my experience. I just had my car in for some dyno testing on Friday including intake testing versus stock, and a few other knick knacks to verify the car is healthy for bigger mods (much bigger turbos, blah blah), as well as to verify I have enough fuel up top, look at fuel trims, if there's timing retard, knock, etc..
Anyway, yea. It seems kind of odd in your case from the graph you show. How many miles on the car, and do you have either AFR or EGT data up top? Or even a decent scan tool log showing timing being pulled or knock, etc..? Any chance the spark plugs are loading up or your coils crapping out or experiencing higher RPM breakup?
had weistec run it on their dyno, some traction issues even with 305s so the car was run in fifth. AFR, spark, fuel trims were all normal. It has brand new plugs, coils, and a few other items. No knock at all. My car has 30k miles and is in really good health. Weistec had it for 3-4 days road testing and verifying everything 🤷♂️. I was thinking about the intakes you have or modalworks. How do you like them?
[QUOTE=domjansson;8543764]had weistec run it on their dyno, some traction issues even with 305s so the car was run in fifth. AFR, spark, fuel trims were all normal. It has brand new plugs, coils, and a few other items. No knock at all. My car has 30k miles and is in really good health. Weistec had it for 3-4 days road testing and verifying everything 🤷♂️. I was thinking about the intakes you have or modalworks. How do you like them?
bms seems to have similar results as me
******The BMS intakes work well on my so far pretty stock setup. I really like the way they look. I bought them to increase airflow once the new turbos go on the car and I get it all properly tuned. Even stock, the car at least sounds a lot better and you can hear the turbos sucking in air, etc.. They were very easy to install and come off easy enough so it should somewhat speed up the turbo swaps to be done soon.
There is, according to the dyno, an increase in performance over the stock air box which I tested as well, before installing the BMS. The stock airbox flows quite well and is a decent match for the stock turbos, which are somewhat small and produce gobs of lower end torque. I expect the intakes to be more helpful for my build once the larger turbos go in and a proper tune is done. The new turbos should shift the torque/HP curve up a fair amount so the extra air flow from the intakes should presumably help some versus the stock air boxes which may or may not be able to keep up at the higher rpm, higher boost potential that larger turbos can provide on a properly matched system with a decent dyno tune.
had weistec run it on their dyno, some traction issues even with 305s so the car was run in fifth. AFR, spark, fuel trims were all normal. It has brand new plugs, coils, and a few other items. No knock at all. My car has 30k miles and is in really good health. Weistec had it for 3-4 days road testing and verifying everything 🤷♂️. I was thinking about the intakes you have or modalworks. How do you like them?
bms seems to have similar results as me
******The BMS intakes work well on my so far pretty stock setup. I really like the way they look. I bought them to increase airflow once the new turbos go on the car and I get it all properly tuned. Even stock, the car at least sounds a lot better and you can hear the turbos sucking in air, etc.. They were very easy to install and come off easy enough so it should somewhat speed up the turbo swaps to be done soon.
There is, according to the dyno, an increase in performance over the stock air box which I tested as well, before installing the BMS. The stock airbox flows quite well and is a decent match for the stock turbos, which are somewhat small and produce gobs of lower end torque. I expect the intakes to be more helpful for my build once the larger turbos go in and a proper tune is done. The new turbos should shift the torque/HP curve up a fair amount so the extra air flow from the intakes should presumably help some versus the stock air boxes which may or may not be able to keep up at the higher rpm, higher boost potential that larger turbos can provide on a properly matched system with a decent dyno tune.
Anyway, for what it's worth.
I assume you have downpipes and a tune as well? That’s awesome! Out of curiosity what did you make with the bms intakes?
I assume you have downpipes and a tune as well? That’s awesome! Out of curiosity what did you make with the bms intakes?
*****My car is completely stock right now except for the new intakes seen in the pic, and Modal Works blow off thing a ma hoochies you can see as well towards the front of the engine compartment. I purposely did not do a tune, or anything else for the purpose of baselining the car. The car will be retested in a week with a base dyno tune to verify fuel trims as well as insure the fuel system is up to spec before I install the bigger turbos, and dyno tune it all again with the new parts I have sitting in a box in my garage. I also have a methanol injection system in a box that I might or might not install contingent upon AFR and EGT values on a mild street tune once the new turbos are on the car. The methanol injection, if I actually end up installing it might be needed for my purposes down the road when I take the car to our local tracks here in my area (Cecil track, Capitol, etc.. for those in the DMV area of the US). I have certain ET goals and trap speeds I wish to reach, but don't want to start messing with the exhaust and possible CEL codes, etc.. My goals are very conservative and I tend to plan a project and test along the way to verify versus just slapping everything on and hoping for the best.
The BMS intakes were worth 15 HP on *my* stock car over the stock airboxes, tested the same day. The runs were *not* banzai runs and I think the final pulls were in 4th gear. The car seemed to have more, and the intakes are really nicely made IMO at a reasonable cost point. No question the intakes will help the car breathe better once the other modifications and tuning are optimized. The purpose of the initial pulls was for the tuner to have an idea on fuel trims, etc.. for his initial dyno tuning, etc.. I'm thinking the intakes had a bit more in them, but who knows as we did limited runs with my car for reasons other than testing an intake..
Stock turbos.
Even the stock housing “hybrid” turbos like the popular Pure options, and others, flatten out or taper off in higher RPM’s.
I am not saying that as a knock to them, just what is happening, and it can have its advantages and disadvantages depending on what your intended usage is.
You can go to a larger housing turbo, like the Premier Tuning Group PTG1000’s for example, and you will continue climbing in power all the way to redline. You’ll have to adjust to the change of the power curve as you won’t have instant punch down low. That isn’t always bad either…..
Example, people sometimes comment to me about preferring a tuned car on Pure 900/1000. Those people may be more “red light to red light” and not often or ever stretching the legs of the car. But with that instant punch in the lower RPM’s with the increased power levels (even experience this on completely stock turbos with a tune)……I often see that as a negative impact as it makes the car much more of a handful down low, where the more linear power delivery of the big turbo makes the car easier to power out, and also makes much more power up top.
Stock turbos.
Even the stock housing “hybrid” turbos like the popular Pure options, and others, flatten out or taper off in higher RPM’s.
I am not saying that as a knock to them, just what is happening, and it can have its advantages and disadvantages depending on what your intended usage is.
You can go to a larger housing turbo, like the Premier Tuning Group PTG1000’s for example, and you will continue climbing in power all the way to redline. You’ll have to adjust to the change of the power curve as you won’t have instant punch down low. That isn’t always bad either…..
Example, people sometimes comment to me about preferring a tuned car on Pure 900/1000. Those people may be more “red light to red light” and not often or ever stretching the legs of the car. But with that instant punch in the lower RPM’s with the increased power levels (even experience this on completely stock turbos with a tune)……I often see that as a negative impact as it makes the car much more of a handful down low, where the more linear power delivery of the big turbo makes the car easier to power out, and also makes much more power up top.
What he said... all turbos flatten out at some point. It is the fundamental difference between turbos and super chargers. Power delivery curve. I prefer SC over turbos, IMHO it is more linear all the way to redline.
I appreciate the responses! Threw on new intakes, got a race fuel tune, gonna re-dyno and see if there are any improvements. I’d rather stay on stock turbos. The car is perfectly optimized for the street racing that I do minus falling off so much in the top end. I did come from a supercharged platform so I guess I did not expect this. I have seen other stock turbo cars pull on me (FBO e30 m4) in the top end but lose from a stop. I just find the power curve interesting. I find myself short shifting at about 5k to win 🤷♂️
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