How Much Boost Can I Take?
08-09-2003, 06:33 PM
#1
Junior Member
Thread Starter
Join Date: Jul 2003
Posts: 7
I have a 88 T2 with the following mods: 255lph walbro fuel pump w/rewire,SAFC, RB Full Turboback 2.5" exhaust. Aluminum 3" TID built by Banzai racing, FCD, Dynotune EGT gauge, Spearco Boost/Vac gauge, autometer water temp, A/F, and volt gauges. Greddy TT. Magnecor 8.5" wires, K&N cone filter, S5 Turbo w/Ported wastegate.Turbo XS MBC,no emissions,no BAC,no thermowax,TB Mod, No A/C, engine just rebuilt by kevin landers using Atkins Rotary rebuild kit. My question is how much boost can a stock internal 13bt engine take? I know that the s5 turbos stock can only goto 14psi I think. I am getting ready to upgrade my secondaries to 720cc Greddy Injectors and I am already boosting to 9-10lbs. and I am curious just how far I can go boost wise with my setup? I ran a dismal 14.9 in the 1/4 with a 97 trap speed. And this is not accpetable to me. Also anyone with a similar setup that I am running could give me some pointers on my SAFC settings for both lo and high throttle maps would be nice. Thanks guys
08-09-2003, 08:24 PM
#2
Junior Member
Join Date: Aug 2003
Posts: 23
ok first say what turbo u have if is the stock one ok i am gonna tell u something i have i 86 rx-7 gxl and i made turbo i have high compression rotors and some people tell me taht it is not gonna last
because is a high compression engine i put everything new from the housing to the rotors and all of the inside of the ingeni i bought from racing beat is bright ported and i am boosting 18 pounds on the stock turbo now when i was boosting 10 pounds i ran 13.02 the 1/4 mile 103 miles of speed u maybe are running to rich or something is going
wrong i have gxl-se ingectors insecondary but i have to extra ingector one at 12 and the other at 16 pounds i am gonna say something
with 18 pounds of boost is good and enought i don't recomend you more than that i don't know how fast my car is running now but bmw
and corvette with nos can't cacht my *** !!!!!!!!!!!!!!!!
the honda eater
because is a high compression engine i put everything new from the housing to the rotors and all of the inside of the ingeni i bought from racing beat is bright ported and i am boosting 18 pounds on the stock turbo now when i was boosting 10 pounds i ran 13.02 the 1/4 mile 103 miles of speed u maybe are running to rich or something is going
wrong i have gxl-se ingectors insecondary but i have to extra ingector one at 12 and the other at 16 pounds i am gonna say something
with 18 pounds of boost is good and enought i don't recomend you more than that i don't know how fast my car is running now but bmw
and corvette with nos can't cacht my *** !!!!!!!!!!!!!!!!
the honda eater
08-10-2003, 04:02 AM
#3
Senior Member
Join Date: Nov 2002
Location: Okinawa, Japan
Posts: 602
If people think that 15 or 20psi is a lot of pressure, they should figure out how much pressure is generated in the engine everytime the fuel gets ignited. It's a lot more than any turbo will be making.
As long as the a/f ratio is good and detonation is under control (good fmic, proper timing, some other variables, yada, yada, yada), the engine will take a lot of boost. But other factors come into play that seem to be practical limiters. It's all in the tuning.
With good tuning, hi-comp rotors will last with boost. The people that say it will not are not speaking from experience. Or even second hand experience. Too much bad info is spread on the forums. Not enough people plan out their mods and take care of the tuning on a dyno with a wideband O2 sensor.
As long as the a/f ratio is good and detonation is under control (good fmic, proper timing, some other variables, yada, yada, yada), the engine will take a lot of boost. But other factors come into play that seem to be practical limiters. It's all in the tuning.
With good tuning, hi-comp rotors will last with boost. The people that say it will not are not speaking from experience. Or even second hand experience. Too much bad info is spread on the forums. Not enough people plan out their mods and take care of the tuning on a dyno with a wideband O2 sensor.
08-10-2003, 12:40 PM
#4
Senior Member
Join Date: Oct 2002
Posts: 1,019
tuned right you should technically be able to run 20+psi on a stock engine. Now the problem that i see is this, you've got the stock computer, running stock injectors (with an AFC) and the top mount IC. With my setup at 10psi with a front mount, i was seeing the A/F getting to above 12.5:1 above 6k rpm. That was enough for me to limit myself to 6k until i got injectors. Above 10psi the stock turbo isn't really very efficient (read as, puts out alot of heat). With the top mount this can create a problem because even if your A/f and timing is fine, if your intake temp is too high, it'll still detonate. Above 10psi you won't gain much HP but you will pick up a bit of torque. Also 97mph trap speed on a better launch would be alot better than a high 14.
08-10-2003, 01:15 PM
#5
Junior Member
Thread Starter
Join Date: Jul 2003
Posts: 7
well my rotors and all that are still the stock ones. and yes my turbo is a stock s5 turbo. I am just trying to get my car into the 13's. Now I have a egt gauge mounted in the DP beside the o2 bung, and I am seeing temps around 780 celsius at wot. I have my SAFC richening 11% on the high throttle map, but I know that I am probably at my limit with my stock injectors cuz I am running out of pulsewidth. That's why I am upgrading to the 720s. I have my timing set to the FSM, it's not advanced or retarded from the factory settings. I am just asking about upping my boost 1 or 2 more pounds to run a little quicker 1/4 mile times now that I will have the fuel system to handle it. My 60 foots were pretty sad as well, they were like 2.4.
08-10-2003, 01:31 PM
#6
Senior Member
Join Date: Aug 2001
Location: Lynnwood, WA
Posts: 3,097
You should be putting out a nice amount of power as it sits now. I would guess with your mods, you should be in the high 13's or low 14's. I didn't have **** done to my AE and it ran a 13.2 @ 106. How many miles are on your engine?
08-10-2003, 03:37 PM
#8
Junior Member
Thread Starter
Join Date: Jul 2003
Posts: 7
the engine only has 2500 miles since the rebuild, and the turbo is brand new. Kevin charged me 1400 for the entire rebuild, including his smaller streetport. He was very nice to work with, and seems to know his stuff. I am happy with the engine I got back and it runs really good. well help me out with my driving skils, what am I doing wrong? I left the line at about 3500rpms i was shifting around 6500rpms. I don't know what the deal is, but it sucks only running 14's....I thought for sure with my mods I would be in the 13s....
08-10-2003, 04:22 PM
#9
Senior Member
Join Date: Dec 2001
Location: Jensen Beach, FL / Sylva, NC
Posts: 2,934
For what this is worth.
I had 720 secondaries and a SAFC and a Profec B. I had a hybrid T-04E turbo which is basically a series 5 turbo with new guts and a ported wastegate. I had a full open exhaust and an intake too. Those were all my mods. I set my profec B to 10 PSI of Boost. I normally run 7 PSI. At 10 PSI I had 250RWHP.
I ran a 13.08 with that. I used my Visctoracer Autocross tires in the rear 245/45/17 and ran my street tires in the front 225/45/17 Toyo Proxes. My front tires were overinflated to 40PSI and my rears were at 16 psi.
My 60' time was 1.9 seconds.
With my new engine I cannot get the car down that low in the 60' time I can only get it to 2.0. This kills your 1/4 times.
You sound like you will be running a pretty close setup to my old one. You really need to get on a dyno and tune the car. Make sure your A/F ratios are cool.
I had 720 secondaries and a SAFC and a Profec B. I had a hybrid T-04E turbo which is basically a series 5 turbo with new guts and a ported wastegate. I had a full open exhaust and an intake too. Those were all my mods. I set my profec B to 10 PSI of Boost. I normally run 7 PSI. At 10 PSI I had 250RWHP.
I ran a 13.08 with that. I used my Visctoracer Autocross tires in the rear 245/45/17 and ran my street tires in the front 225/45/17 Toyo Proxes. My front tires were overinflated to 40PSI and my rears were at 16 psi.
My 60' time was 1.9 seconds.
With my new engine I cannot get the car down that low in the 60' time I can only get it to 2.0. This kills your 1/4 times.
You sound like you will be running a pretty close setup to my old one. You really need to get on a dyno and tune the car. Make sure your A/F ratios are cool.