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((And I just got this email from BOFI racing... Makes me consider just dropping this turbo in and calling it a day, but then I'd be worried about the spool with the 2.5" exhaust. Newaza, how would you describe the spool on your eBay manifold? I'm under the inpression that my setup sucks nuts for spool, and quite frankly power too.))
Mine is a bit of a different animal. It is set up for 1/8th mile drag racing and uses an automatic transmission. I artificially spool mine with an onboard compressed air setup, so when I use that system it spools very quickly. Without that air system it is a dog out the hole. My manifold is hogged out so missmatch to turbine inlet is not an issue. In so far a power goes, I've trapped 109.8 mph in the 1/8 mile. Most calculators say that takes about 525 hp or so to run that at my weight. I'm sure a well designed tubular will make a little more, but bang for the buck those cheap manifolds are hard to beat. The turbo I use mostly is a gtx3576 sized churbo with a .82 ar housing so it will never spool well on a 1.8l 4 banger without artificial help such as compressed air or nitrous. Without artificial help to spool you could floor mine at 2pm on tuesday and maybe have full boost by breakfast on wendsday LOL....
((And I just got this email from BOFI racing... Makes me consider just dropping this turbo in and calling it a day, but then I'd be worried about the spool with the 2.5" exhaust. Newaza, how would you describe the spool on your eBay manifold? I'm under the inpression that my setup sucks nuts for spool, and quite frankly power too.))
Mine is a bit of a different animal. It is set up for 1/8th mile drag racing and uses an automatic transmission. I artificially spool mine with an onboard compressed air setup, so when I use that system it spools very quickly. Without that air system it is a dog out the hole. My manifold is hogged out so missmatch to turbine inlet is not an issue. In so far a power goes, I've trapped 109.8 mph in the 1/8 mile. Most calculators say that takes about 525 hp or so to run that at my weight. I'm sure a well designed tubular will make a little more, but bang for the buck those cheap manifolds are hard to beat. The turbo I use mostly is a gtx3576 sized churbo with a .82 ar housing so it will never spool well on a 1.8l 4 banger without artificial help such as compressed air or nitrous. Without artificial help to spool you could floor mine at 2pm on tuesday and maybe have full boost by breakfast on wendsday LOL....
Keep stock cam gears. With a non-shitty turbo setup, they’ll make 300+ all day. then there’s no question if they’re timed wrong. No need to **** with it for marginal gains. If your turbo setup is shitty, you shouldn’t be trying to find more power with cam timing anyways.
Which brings me to my next point, your turbo setup is probably shitty. You can never have more torque than horsepower above 5250rpm. If you’re making peak torque at 5000, it means your spooling incredibly late. My 6758 spools pretty late, but makes peak of 280ft/lbs around 4250rpm, and goes on to make ~330ish from 6000 to 7000. Post your graph, my guess is you’re combining a really slow spooling turbo with a really restrictive exhaust, which is making your spool even worse, then choking off the top end.
Keep stock cam gears. With a non-shitty turbo setup, they’ll make 300+ all day. then there’s no question if they’re timed wrong. No need to **** with it for marginal gains. If your turbo setup is shitty, you shouldn’t be trying to find more power with cam timing anyways.
Which brings me to my next point, your turbo setup is probably shitty. You can never have more torque than horsepower above 5250rpm. If you’re making peak torque at 5000, it means your spooling incredibly late. My 6758 spools pretty late, but makes peak of 280ft/lbs around 4250rpm, and goes on to make ~330ish from 6000 to 7000. Post your graph, my guess is you’re combining a really slow spooling turbo with a really restrictive exhaust, which is making your spool even worse, then choking off the top end.
Yeah, you're right about not ******* with the adjustable cam gears, but I've already done an Exhintake cam swap and I think my cam timing is off due to poor drilling of the hole. At the time of writing my last post I wasn't sure if I had the exhaust cam advanced or retarded, but after looking into it, I think I have it slightly retarded from the 197.5 deg offset people normally use. The hole was drilled small due to not having the correct bit and slightly high due to my own error, and then we enlarged it in very small increments until we had a tight fit. Most of the material was take from the bottom right side. With it being slightly retarded, it probably isn't helping spool, but it still shouldn't spool up that late with only a 2560R. I've seen online where both the intake and exhaust cam gear on the non-mazdaspeed BP4Ws have the little timing protrusions, so when I get around to fixing my front main seal leak I will look into swapping the cam gears and redrilling the hole more accurately. I only considered getting adjustable gears since some of them like the (now discontinued) KAInjection gears come with a hole pre-drilled for the exhintake mod AND the timing protrusions for the BP4W sensor, but unfortunately I've not been able to find any for sale online. I'm not a huge fan of drilling into brand new adjustable gears simply because I don't want to waste a ton of money on a dyno for the tiny bit of HP gains that might come with it. I don't think street tuning with VD would be accurate enough in these Tennessee hills.
I'll get around to posting the virtual dyno graphs later tonight if time allows. I'd like to take a new data log today and show a few separate gears. I was thinking a pull in second gear and third gear from 2000rpms or so for the transient response, and then an additional pull in 5th until I see peak boost for the minimum boost threshold. VD might not be the most accurate for numbers either since I use 2450 for the cars weight since that is what it weighed when I measured it last time. I'm not 100% sure what I had done to the car at the time though. I think 2450lbs was with a half tank of gas, no turbo, A/C, power steering, a rollbar, and 205/50/15 tires on the stock wheels. Not sure if I was sitting in the car or not though. Maybe someone with an NB could chime in on how much theirs weighed? I no longer have A/C or PS but now have a turbo and all of that fun stuff.
Anyways, rambling aside, I believe my biggest issue is the T25 flange on the turbo and the T3 flange on the manifold. The T25 flange (excluding the fillets) has an area of 1873.4 mm^2 and the T3 flange (again excluding the fillets) has an area of 2556.8 mm^2, which means ~27% of the area of the T3 flange is met with a abrupt wall and forced to flow through an area 73% smaller than what it is already in. I'm no expert in fluid dynamics yet it's pretty obvious this is terrible for flow, and it could account for the poor spool and top end performance both. I've already done testing in another thread to see if my muffler was the restriction and I gained no additional power by taking the muffler off, so the biggest restriction/impedance to flow is likely before the turbine. I'm not a huge fan of porting this turbo either since I planned on getting rid of it soon and that could hurt its resale value. If I were to sell the manifold, turbo, and downpipe all together it wouldn't matter though... I'll think about it, but in the meantime here's a comparison of the flanges' dimensions from Garrett's website:
So... Saturday I drove 30 minutes to the closest E85 station which happened to be in Bristol, VA. I had the tank as empty as possible and filled it up with 11 gallons of E85. Tuned it right there and then, and oh boy. E85 is amazing. Not only did I gain 400rpms of spool time (in 4th gear), but VD is showing gains of 70 lb-ft and 55 hp at the wheels. This put it at ~275 whp and 300wtq according to VD with a 2400lb car and a 200lb driver. I'll post the VD later today or whenever I get a chance. I'll definitely be running this for autocross and drag races moving forward.
Speaking of autocross, I had one yesterday and the extra torque and quicker spool made the car so different to drive. I ended up leaving the line in 2nd gear and going into 3rd just to keep from spinning haha. If my tires weren't shot, I believe the car would be much more composed. The Maxxis VR-1s in 245 weren't the fastest even when new, but now that I'm at both wear bars and plenty of camber wear it is getting pretty rough (plus the date code on the tires is mid-2019). It's been a long time since I've looked at tires, but if anyone has input on 200tw 245s for autocross I'd be happy to listen. I'm currently planning on picking up Rival S 1.5s when the new season runs around. After driving down there and autocrossing, I filled up the tank with more E85 to make it home and it turns out I got 18 mpg which isn't too bad.
Lastly, I am taking the car over to my grandparents to attempt to port-match the manifold and turbo. The plan is to get it all back together before the weekend. On Saturday, Bristol Motor Speedway is hosting their last "Street Fights" drag night. I should be able to get 5-10 passes in and I'm really hoping to see 12 seconds, but I don't know how realistic that is. Maybe after porting the turbo's housing, it'll pick up some more power.
What a week this last week was. After that autocross, I immediately began tearing down the turbo system. I took off the turbo to port match it to the manifold's T3 hole and ported out the manifold while I was at it. Pics attached:
Not the prettiest job, but it'll do. After this, I did a virtual dyno run for a before and after. I'm not sure how accurate the weight input is, but it was kept constant so it will at least be precise, even if inaccurate. One note is that the pump gas pull was done in 3rd gear. I had a few in 4th but this one was a good middle ground (some of the others read higher and some read lower). AFRs on the gasoline pull were rich, while the ported ethanol run was lean. I was still tuning it when I did this pull. I didn't hear any knock through the headphones so I stayed in it despite it being slightly lean.
The blue run was pump gas, red was e85, and green was e85 with the ported manifold. All had the same boost controller duty cycle.
After this, I went on to run at the Bristol Street Fight drag races. I easily beat a Chevy Tahoe, a 4.0 Ford Ranger, and a '97 SVT Mustang (even though I butchered the launch and miss-shifted twice I chased him down at the 1000' mark). I did not win against the supercharged 5.0 Mustang that ran an 11.2 though, haha. The best run was 13.3@108mph with a shitty 2.2x 60 foot. I'd like to think with more runs I would've been able to do better, but with the 500tw all seasons I was very grip limited. When winter comes around I plan on swapping in my 3.63 gears (I've got a 4.3 right now) and reinforcing the housing at the same time. I'm hoping that'll be strong enough to let me run some drag tires and get into the 1.9s in the 60-foot or better. The M&H 7.5/23.0-15 tires with the 3.63 and a rev limiter of 7500 will get me to 112 mph in 4th according to the online gearing calculators. Any input on if that much grip will start breaking things?
08-02-2023, 02:37 PM
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