rztmartini Posted August 31, 2006 Share Posted August 31, 2006 Ok so I am reading up a lot on turbos and calculating the flow rate of my engine and the pressure ratio so I can read a compressor map. the problem i keep having is that when i hit full (planned) boost at around 3000 rpm, the point is almost always above the surge line. if i actually run a turbo with this compressor map, what will happen? will the point just follow the surge line until it reaches the desired pressure? Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted August 31, 2006 Share Posted August 31, 2006 you'd be using the wrong turbo. It would have a host of problems and my guess it the turbo would be short lived. Buy corky bells book or learn how to properly select a turbo from many of the online turbocharging folks like ray hall. You need to find a turbo that your in the sweet spot most of the time if not all the time with peak efficiency or near that at your full boost level. Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 31, 2006 Share Posted August 31, 2006 As Dr Hunt says "you'd be using the wrong turbo". For you to make full boost at 3000 rpms is pretty low, even in 5th. Your hotside would be on the small side. Do you really need full boost that low. How much for you is full boost? If you are in the surge area, you will stay in it until the engine can use the air to get you out of it (more rpms). Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 31, 2006 Share Posted August 31, 2006 I'm running a T04B-H3 compressor with boost starting at 3000 and hitting max pressure by 3500 rpms. I really should had used a different compressor but this one was cheap and easier to install. When looking at the compressor maps, this turbo should be surging, but it doesn't. It runs fine so I'm not going to mess with it. The maps aren't always 100% correct. What compressor are you using? My stock T3 would start boosting a little at 2000 rpms and reach full boost by 2800 rpm. The huge low speed torque made the car very fun and easy to drive on the street. Tons of torque in every gear! But the top rpms were limited to around 5300 rpms due to the small turbine. Sure, my new turbo is faster, but I do miss the low speed torque and the instant responce of the smaller turbine. I guess it all depends on your driving style. Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted August 31, 2006 Share Posted August 31, 2006 What compressor are you using? One option is to use elec boost control to gradually increase the boost limit with rpm so you never get into surge. Thats what I plan on doing. You also get the added benefit (well a benefit with a new garrett BB turbocharger) that boost doesn't hit quite as hard. Makes it a lot more controllable. Dave Quote Link to comment Share on other sites More sharing options...
rztmartini Posted August 31, 2006 Author Share Posted August 31, 2006 I am looking at the To4E 50 trim. i was using the 3000 rpm full boost (14 psi) as sort of a lower limit. is that not realistic? if i were to get an electronic boost controller, it would sort of stall full boost untill i wanted it or what? I have read the entire "Max boost" by corky bell...although it was a couple months ago. maybe i should refer back to it... Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 31, 2006 Share Posted August 31, 2006 I am looking at the To4E 50 trim. i was using the 3000 rpm full boost (14 psi) as sort of a lower limit. is that not realistic? if i were to get an electronic boost controller' date=' it would sort of stall full boost untill i wanted it or what? I have read the entire "Max boost" by corky bell...although it was a couple months ago. maybe i should refer back to it...[/quote'] The turbine side also plays a big part in spool. I think it would only be realistic to achieve 14 psi by 3k if you had a stock turbine wheel with a .63 hotside, which you wouldn't want to do if a power increase was your goal. I ran a V trim that surged a bit earlier than an E50. At 14 psi it happens about 6 lb/min sooner, similar to Pyros. I didn't have any problems on the street either. I could get it it do it on the track on long turns with lower rpms with part throttle but that would never happen on the street. I wouldn't worry to much about surge at 3k. Even if you could make it into that side of the map, you would only be there for a split second. It's different when you are in the surge area for extended time. Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 31, 2006 Share Posted August 31, 2006 Look at the compressor map of a T04B-H3 wheel and you will see it is much worst than a T04E 50 trim on a 2.8 liter engine. And, I don't get any surge. I think you will be ok. You can get full boost by 3000 rpms if you use a stock exhaust turbine or maybe just one stage up. The problem is, the stock exhaust turbine will hurt top end power. But it makes much better low speed torque. If I had to do it over again, I would use a exhaust turbine that spools up more like a stock turbo. But maybe that is why my T04b-H3 works because full boost comes in at 3500 rpm instead of 3000. I have read the T04E 50 trim should be the ideal turbo compressor for a 2.8. You will need an 1/2 inch spacer to use that turbo on a stock exhaust manifold. Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 31, 2006 Share Posted August 31, 2006 I have read the T04E 50 trim should be the ideal turbo compressor for a 2.8. Ideal depends on airflow and boost. At 14 psi it would work, at 25psi it would be way too small. Quote Link to comment Share on other sites More sharing options...
rztmartini Posted August 31, 2006 Author Share Posted August 31, 2006 ok thats exactly what i wanted to know. i am using the car for 90% street and autoX, i really doubt i will ever do any track racing, thats why i went with the .63 A/R turbine for quick spool and more torque. top end HP is my last concern, compared to reliability of the engine and that much street use. the 14 psi boost will be my max, as my engine could not be able to handle much more than that combined with my total noob tuning skills. so if the turbo hits the surge limt for a split second while boosting x the amount i will be driving it, will this be damaging to the turbo in the long run? Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 31, 2006 Share Posted August 31, 2006 so if the turbo hits the surge limt for a split second while boosting x the amount i will be driving it' date=' will this be damaging to the turbo in the long run?[/quote'] For a second, no. If you are doing 5th gear pulls from 2k or towing with full boost at low rpms that's different. Have you figured out the enigine flow at 3000-3500 rpms at a 2.0 PR? What did you come up with? After about 8 years I finally wore the thrust bearing enough that it need to be replaced. Quote Link to comment Share on other sites More sharing options...
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